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APRIL 



EXTRA 



17}p(3B; 



n 




_ HIGH 
:W) IMPEDANCE 
"^ VOLTMETER 



ADCOLA Soldering 
Instruments add to 
your efficiency 



ADCOLA 64 

for Factory Bench 
Line Assembly 

A precision instrument — supplied 

with standard 3/1 6" (4.75 mm) 

diameter, detachable copper 

chisel-face bit*. 

Standard temp. 360°c at 23 

watts. 

Special temps, from 250°c— 

410°c. 

'Additional Stock Bits 



(illustrated) available 



COPPER 




B 58 "i " — 6.3* mm chisil FACE 

LONG LIFE 

I ^~7? 

B 42 LL -fV' «7Smm CHISEL FACE 



CHtSEL FACE 




Don't take chances, We don't. 
All our ADCOLA Soldering 
Instruments are of impeccable 
quality. You can depend on 
ADCOLA day after day. That's 
why they're so popular. You get 
consistent good service . . . relia- 
bility . . . from our famous therm- 
ally controlled ADCOLA Element 
and the tough steel construction 
of this ideal production tool. 



Write for 
price list 
and 

catalogue 
ADCOLA PRODUCTS LTD., 

<Dep£. M) r ADCOLA HOUSE, GAUDEN RD„ LONDON, S.W.4. 
Telephone: 01-622 0291/3 • Telegrams: Sol joint London Telex •Telex: Adcola London 218&T 





for fast, easy, 
reliable soldering 

Contains 5 cores of non-corrosive 
flux, instantly cleaning heavily 
oxidised surfaces. No extra flux 
required. 



SAVBIT ALLOY 
ALSO REDUCES 
COPPER BIT WEAR. 

Ecomically packed for 

general e ectrical 
and electronic 
soldering. 75ft 
18 gauge on 
plastic reel. 
Recommended 
retail price 75p 




A RANGE OF 
SOLDERS IN HANDY 
DISPENSERS. 



INVALUABLE FOR STRIPPING 
FLEX, THE NEW AUTOMATIC 
OPENING BIB WIRE STRIPPER 
AND CUTTER, easily 

adjustable for all 
standard 

diameters. Plastic 
covered handles 
can also be used 
as wire cutter. 
Recommended 
retail price 50p 



From Electrical and Hardware shops. If unobtainable, write to: 
<5§> Multicore Solders Ltd., Heme) Hempstead, Herts. 



REF. ALLOY SWG 


!**' 


4 A 60/40 


18 ISP * 


., 


Size5 

ustra- 1 -"" u " 
ted) 
15 60/40 


18 ISp • 

22 20n * 


ii-w 


* Recommended Price 


. 



THIN GAUGE 
SOLDER, 
ESSENTIAL FOR 

soldering small components 
and thin wires. High tin 
content, low 
melting point, 
60/40 alloy, 170ft. 
22 gauge on 
plastic reel. 
Recommended 
retail price 75p 





EX-RENTAL TELEVISIONS 
TWO-YEAR GUARANTEE 



17* SLIMLINE 
£11.95 

19 SLIMLINE '105/625 
£29.95 

Carriage and Insurance £1.50 

FREE ILLUSTRATED LIST OF 

TELEVISIONS 

17"— 19"— I r— 23" 

WIDE RANGE OF MODELS 
DEMONSTRATIONS DAiLY 



SPEAKERS SOnp, U' Bfl, 4' IOC! 
BRAND NEW P. & P. K'np. 

Traniittorn Milliard m itched output 
kit 37np. OC6ID— IOCS!**. P. A P. 

FREE. 

Transistor Radio Cats:;: 25 np each. 
Size 9+" x 6±" x 8jp. F. & P. I 5np. 

Ferrite Rods 1 7 rip: 6" 3rd 7" complete 
with LW/MW Coil*. P & P. FREE. 

PRESS BUTTON SWITCHING 

UNITS, 4 Banks I7np, li Banks 27np. 
P. & P. 5np. 




TV TUBES REBUILT 
GUARANTEED 2 YEARS 




1 4'— £3.95 17- & 1 9'— £5.95, 

21" &2J"— £6.45. 

Exchanged Bowls. Carr. 60np. 



(DUKE & CO. LONDON) LTD. 

621/3 Romford, London, E12 

TeJ. 01-478 6001/2/3 



GOMPL 




FOR ONLY 



£4095 




PREMIER STEREO SYSTEM "ONE" Consists of an all transistor stereo amplifier. Garrard 2025 T/C auto 
manual record player unit fitted stereo mono cartridge and mounted in teak finish plinth with perspex cover 
and two matching teak finish loudspeaker systems. Absolutely complete and supplied ready to plug in and play. 
The 10 transistor amplifier has an output of 5 watts per channel with inputs for pick-up, tape and tuner also 
tape output socket. Controls: Bass, Treble, Volume, Balance, Selector. Power on off, stereo mono switch. 
Brushed aluminium front panel Black metal case with teakwood ends: Size 12 x 5± x 3im. high (Amplifier 
available separately if required £14.95 Carr, 40p.) NOW AVAILABLE - MATCHING FM TUNER £22.0$ 



PREMIER STEREO 
SYSTEM "TWO" 

As system 'ONE' above 
but with Garrard SF2i. 

PREMIER t* A -j Carr. 
PRICE *»*»/ £1,75 



MIDLAND AM/FM STEREO TUNER AMPLIFIERS 



Two new all solid state receivers from Midland at 
economical price*. Beautifully styled in slimline 
cabinets. 



Specification i 
Semi conductors 



Tuning range 




Aerial 



MODEL 19-520 




MODEL 19-520 

19 trans iators, 
12 diodes, 2 varistors 
FM 88-108 MHz 
FM Stereo Multiplex 
AM 635-1635 kHz 
Internal AM and 
external FM 
Frequency response 50-17,000 Hz 
Power output 2J watts rms per 

channel (8 watte 
music power) 
Inputs CeramlG phono 

speaker impedance 4-6 ohm 

CHlttiilliH Power on/off, Volume, 

tone, balance, tuning, 
AFC. Stereo indicator 



Function selector 



MODEL 19-M2 



AM, FM.FM Stereo, 
Phono (Stereo 
ind Icator light 1 
lS'l8tV'*3r 

£30.45 

Carr. A Ins. 50p 



MODEL 19-542 

22 trans istorn, 

12 diodes 

FM 88-108 mHz 

FM Stereo Multiple! 

AM 335-1603 kHs 

Internal AM ami 

external FM 

35-20.000 Hz 

4 watte rms per 

channel (18 watt* 

music power) 

Magnet ic/Ceram ic 

phono and aux. 

& ohm 

On /oil, Volume, bass, 

treble, balance, 

tuning, AFC. 

Stereo indicator 

AM, FM, FM Stereo, 

Ceramic, Magnetic. 

Aux. 

16j' x 9f r 31* 



£44 



Carr. & Tub* aOp 




E.M.I. 13xSin. 
HI-FI SPEAKERS 

Fitted two 2iin tweeters and 
crossover network. Impedance 
8 or 15 ohm. Handling capa- 
city 10W, Brand new. 

& P. 40p 



£3.47 




HI-FI STEREO 
HEADPHONES 

Designed to the highest 
possible standard. Fitted 
2jin speaker units with 
■oft padded car muffs. 
Adjustable headband. 
d ohms impedance. Com- 
plete with 6 It lead and 
stereo jack plug. 
IT. & 
25p. 



STEREO STETHOSCOPE SET Low imp. UM 

P. A P. lOp. 

MONO STETHOSCOPE SET Low imp. 52n. P. A P. lOp. 



VERITAS V-I49 MIXER 

Battery operated 4-channel audio mixer providing lour 
separate Inputs. Silo 6 X 3 x 2in. suitable lor crystal micru- 
phone tow impedance micro- 
phone, with transformer, 
radio, tape, etc. Max. input 
1-Sv. Max. output _ mv. Gain 
6 dIJ. Standard jack plug 
socket inputs, phonoplugs 
output. Attractive teak 
wood grain finish case. 



KONO 
MODEL 




£3 



STEREO £ 1 A~I 
MODEL JW.tl 




POCKET SIZE MULTI-TESTER With wide 
angle, jewelled meter movement, ceramic 
long-liie, low-loss switching, tough knpaol 
resisting case. Sensitivity 20,000 ohms/ 
volt D.C. 10,000 ohms/ vol I A.C. 
19 Ranges: 0-8-25-50-250- 600 -2500 volU 
DC. 0-10-50-100-600-1000 volts AC. 
0.50jlA'2fl mA-250 oA DC. 0-6000 ohms- 
6 megohms, 10)* /if-QOOI mfd-1 nifd. 
-20 to +22dB. Complete battery, lest 
lead and £jt QA P. A P. 



instructions. 



17p. 




"VERITONE" RECORDING TAPE 

SPECIALLY MAKTIFACTI7RED IK U.B.A. FROM EXTRA STRONG 
PRE-STHETCHED MATERIAL. THE QUALITY IS UNEQUALLED. 
TENSILISED to ensure the most permanent base. Highly resistant to break- 
age, moisture, heat, cold or humidity. High polished splice free finish. Smooth 
output throughout the entire audio range. Double wrapped-attractlveiy boxed. 

LPS 8- BSD' P.V.C. 88p LPS S|* 1200' P.V.C. uZp 

TT3 S' 430' POLYESTER 37p 
MS SJ' 800' POLYESTEB 57]t 
SP5 5' BOO' P.V.C, 42p 

LPS B- 900' P.V.C. 50p 

DTS S- 1800' POLYESTER T5p 
TAPE SPOOLS 3" lOp, 6", UK. 7' 9p, 
Post and Packing 3' 3p, 6*. aj", 8p, 7* lOp. (3 reels and over Pott Free) 



DTfl 


Si 


■m 


ij 


SP7 


7" 


LP7 


7" 


DT7 


7- 


TT7 


T 



1800' POLYESTER £112 
£400' POLYESTER «-87 
lZOO 1 P.V.O. 62? 

1800' P.V.C. 75p 

£400" FOLYESTEE £1 35 
3800' POLYESTER £2 50 



50 Watt Public 
Address Amplifier 

MODEL PA-5000 

w^>.:.:-:WMW-!< l -.-.-WM*..:!Mlt>>> 1 .., ■-' 1 1 J - - - -*! 




.\ tup mi.iiity amplifier giving 50 watts rms power 
output 180 watts peak). Incorporates 8 transistors 
and 4 silicon diodes (silicon output transistors). 
Inputs fur 8 microphones each with individual volume 
cnntroU, plus radlo/aux input. Master volume control 
and Bass and Treble Controls. Well presented front 
panel for ease of operation, on/oB power flick switch 
and pilot light. Output impedance 4/8/1$ ohms- 
Mike i * 2 sensitivity 2mV (SDK ohm*). Radio/ Anx 
300m V ( tOOKohms). Frequency response 50-20,000 Hz. 
Ftwsd output and thermal overload protection. 
A.C. Mains 220-2.1 0v. 50/60 Hz. Size 13 J* x 9" x 5' 



PREMIER 
PRICE 



£39 



P. & P. 
50p 



SPECIAL OFFER! 




r.ARRARD SP25 MK IT 
SINGLE RECORD 
PLAYER FITTED 
COLORING 850 

MAGNETIC STEREO 
CARTRIDGE COM- 
PLETE IN TEAK 
PLINTH WITH RIGID 
PEHBPEX COVER. 

Total list price over £24. 
PREMIER PRICE 

£18.90 

p. A P.SOp. 




TAPE CASSETTES 



(mio.) 37p 

Cm.) 62p 
(m?n.) 87 P 



3 for 
£1.05 
3 Tor 

SI. Si 



All cassettes eon be tupplied with library caret 
ot 3p. extra each 



TTR 



UL 



10 & 23, TOTTENHAM COURT ROAD, LONDON, W.1 TEL: 01-636 3451/2639 
HEAD OFFICE & MAILORDER DEPT 23TOTTENHAM CT. RD. TEL: 01-636 3451 



985 






DISCOSOUND 



^^^^^^^^^™ J 


I 


_ ■ mscosot/tro «o 

{ S t?\/!W\ ass S 62t\ «ffl ^ 




o o — — © — -— © 


«> -" ji_ -««r Ja» 



DISCOSOUND 40 PRE-AMP 

The Biscosound 40 offers the same speciacation as the D.J. Disco Amp 
without the power output stage. Size 16inx7mx7in. Se f powered and 
ideal for use with the Discosound 100 Power Amplifier below and one of 
the outstanding features is that it is capable of running ten of these Power 
Amplifiers (Total l.OOOW). 

PRICE £40.50 inc. P & P. 



DISCOSOUND 100 POWER AMPLIFIER 

A 100W RMS (8 Ohms) High Fidelity power 
Amplifier which utilises all silicon transistors 
of modular construction and featur.es full 
automatic overload protection against short 
or open circuits. Frequency response 
20-2O,O0OHz± 2dB. The High output is 
ideally suited for discotheques, groups, 
clubs, etc., or anywhere where reliability 
and quality are required. This unit is the 
companion model for use with our control 
pre-amp Discosound 40, or can be used with 
any other high quality pre-amp control unit. 
Completely built and tested on steel Chassis. 

PRICE £49.50 inc. P & P. 





DJ70S 

INTEGRATED 
MIXER- 
AMPLIFIER 

One of the finest units available on the market today, regardless of price. 
The front end of the unit consists of a four channel mixer with separate 
inputs and volume controls, plus a separate bass, treble and master volume 
control. One of the main features of this remarkable amplifier is its 
elaborate protection against short and open circuit and we can guarantee 
that it is virtually indestructible. Allied to this is its very high power 
output (TOW R.M.S.), a frequency response (30-20,OOOHz±3dB) that is 
superb, and distort ionthat is well below 1 % even at full output. The unit 
is suitable for use with discotheques, groups, P. A., clubs, etc, or anywhere 
that high quality high output is required. Size: 15iinX 5inx6m. 

PRICE £63.00 inc. P & P. 



Also available DJ105S 30W PA Amplifier, 
above. 



PRICE £41.00 inc. P & P. 



For full details of these and all Diicosound Products write direct to:- 

DISCOSOUND, 

122 BALLS POND ROAD, LONDON, N.I. 
Telephone : 01-254 5779 

Full money back guarantee if returned within 10 days. 

All Discosound Products are guaranteed for 12 months. 

Demonstrations given at any time. 



Similar specification to 



VALVES 



SAME DAY SERVICE 
NEW! TESTED! GUARANTEED 



DL92. DL94. 
Brt o! # TtoVji"«. INkSe, »*», DK96, DL96,' 4 for £1-45, 



g ETC IBS, 185. IT-,, 334. 3V4, DAF91, BF91, DI 



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12AH8 ££ 


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DF91 


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S7.DL92 

DL94 

DL9S 

DY86 

DY87 

EABC80 

EAF42 

EB91 

EBC33 

EBC41 

FBC90 

IBF80 

FBF89 

I.OCB1 

I;OC82 

110083 

KOC85 

i:CCS04 

KCF80 

ECF83 

15CH35 

15CH42 

:3CH81 

5CH83 

3CH84 

3CLSG 

SCL82 

ECL88 

EF39 

EF41 

EF80 

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EF86 

BF89 

EF91 

EF183 

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EH90 

EL33 

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£L90 



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READERS RADIO 

85 TORQUAY GARDENS, REDBRIOGE, ILFORD, 
ES S EX. T e 1 . 01 .550 7441 . 

Postage oi) 1 valve Bp, on 2 or more vEvtvea 3p per valve extra. 
Any parcel Insured against damage In transit 3p eitra. 




The great new 1 97 1 edi- 
tion of Lisky's famous 
Audio - Tronics cata- 
logue is now available 
— FREE on request. The 
-44 newspaper size pagt s 
— many in full colour-- 
are packed with 1000 s 
of items from the largest 
stocks in Great Britair of 
everything for the Rsdio 
and Hi-Fi enthusiast. Elec- 
tronics Hobbyist, Serviteman 
and Communications Ham. 
Over half the page; are 
devoted exclusively to every 
aspect of Hi-Fi (ir eluding Lasky 
budget Stereo Systems an 
Package Deals). Tape record 
ing and Audio accessor es and 
introduces LASKY'S AUDIO 
TRONICS CREDIT CARD 
SCHEME offering holders one 
months interest free credit u 
to £50. Send your name and ad 
dress and I 5p for post and inclusi 
on our regular mailing list. 
LASKY "S LTD., (Dpfc. P.W.) 
3-15 CAVELL STREET 
LONDON. El 2BN 



986 



ALPHA-ARENA • TELETON • HL .- AMC • KOSS • APOLLO • SHORE • CELESTION 




SME-LEAK*SINClAm*WHAREEDALE*TRIO^LUXOR*PICKERIWG*PHILIPS ETC ETC 



HY PAY MORE ? ALL GOODS ARE BRAND NEW & FULLY GUARANTEED FOR 1 2 MONTHS 




TURNTABLES p.p. 60p 

GARRARD 5100 with Cartridge .... £7.97 

GARRARD 2025 TC with Sonatone 

flTAHC Diamond Cart £1,50 

GARRARD 3000 with Sonatone 

BTAHC Diamond Cart £9.50 

GARRARD A70MKII £16,07 

GARRARD SP25MK3 £18.17 

GARRARD SL65B £12,75 

GARRARD AP7B £19,97 

GARRARD SL72B £25.00 

GARRARD SL7SB , £27.97 

GARRARD 401 £27. SO 

GARRARD SL95B £48.00 

THORENSTD125 £61-00 

PICK UP ARMS pp.35p 

SME 3009.S2 £25.M 

SME 3O012;S2 £27.50 

GOLDRING LENCO L75 , £9 99 

GOLDRING LENCO L69 £8-75 



STEREO AMPLIFIERS p.p. 50p 

H.L. SA707 with Scratch Filter £19.00 

METROSOUND ST20 £27.75 

AMSTRAD BOOQ £20,97 

TELETON SAQ206 £18.97 

SINCLAIR 3000 £35.00 

SINCLAIR 2000 £21.00 

SINCLAIR PRO 00/2 Z30/PZ5 £15,97 

TELETON SAQ 5015 £34 97 

QUAD 303 4 33 £87.00 

ARMSTRONG 521 (Teak cased) .... £43.50 



TUNER AMPLIFIERS pp. 75p 

TELETON MX990 WITH SPKS .... £41.50 

TELETON RBOO WITH SPKS £47.50 

TELETON CR10T WITH SPKS.... £29.00 

TELETON TFS50 £53.50 

TELETON R420Q £33.00 

TELETON F2000 £31.00 

TELETON 7AT1 £81.00 

TELETON R4300 £40,00 

TELETON F23O0 £40.00 

TELETON CR55 £90.00 

TELETON 10AT1 £105,00 

TELETON 7AT20 £78.00 

PHILIPS RH781... £54.00 

A.M.C.7500 7 x ? VHF £31.00 

MIDLAND 19.542 AM-FH MPX .... £31.00 



TUNERS p.p. 50p 

TELETON GT101 £32.07 

TELETON STO 201X £28,00 

TELETON STQ204X £38 XI 

SINCLAIR 2000 £19.00 

SINCLAIR PRO.60 £20,50 

TRIO KT1000 £47.00 



SUPERB PLYNTHS AND COVERS as illustrated 

Suitable lor Garrard ATM, SP2S, 2000, 2500, 3000, 3500, 5100, 2025, 1025, SL65B and B.S.R. McDonald range 
«"&*«** I't!D*1.?i£u ^ :_ r 2 a ^,f u *.„°. r J u ?5 ( I- ll ^ as ? em y. e<I> - Complete with tinted perspex cover. This unft Is 

(£3 ■50 5o P p u !p) 



finished in Teak polish and will blend In any "home. Please state deck' 
when ordering. 

SUPERIOR PLYNTHS AND COVERS for Garrard AP75, AP78. SL72B 
5L75B and SL95B £4.85+[60p p & p (Recommended list price £10 -00). 





A COMPLETE STEREO SYSTEM FOR 

■ ONLY £37.80 




ITS PERFORMANCE CAN BE COMPARED 

WITH EOUIPMENT COSTING AT LEAST £130 

THE APPOLLO 100% MADE IN ENSLAND 

Thla modern compact unit has been specially designed to 
give the maximum stereo performance In your home. 
Slenderly designed, the unit employs the latest Garrard 
2025TC record deck which enables you to play your records 
manually or allow the machine to auto-change up to eight 
records automatically. The Garrard record deck Is fitted with 
a cue and pause control which allows you to manoeuvre the 
arm of the deck to any chosen track of your record. Also used 
It a locking device to prevent the arm from moving whilst 
unit is in transit. 

The amplifier used in this unit will give a true 5 watts (R.M.S.) 
per channel with maximum performance of base and treble. 
The controls are of a simple nature and allow you to adjust 
the balance of sound through each speaker, also the volume 
required, bass and treble. 

The two speaker systems supplied with this audio unit are 
designed to give the best possible sound reproduction, the 
twin cone base unit will give a good baas response and the 
parasitic tweeter employed will clarify the high notes In 
your listening pleasure. 

Finished In teak, this Hf-FI compact unit will blend Into any 
modern home and give you hours of listening pleasure In 
true stereo. 12 month* guaranteed SPECIFICATION. Deck— 
Garrard 2025TC. Cartridge— Garrard G.C.538 with sapphire 
stylus. Output 5 watts (S.M.S.) per channel. Frequency: 
40Hz to 20,000Hz. Speakers: Apollo 05 Three-way general 
purpose 15-16 ohms. 6" Twin cone bate unit: 2+" Parasitic 
Tweeter: LC Crossover; Suitable acoustic padding. Finish: 
Polished teak plinth and speaker cabinets: Charcoal tinted 
Perapex cover; Unit finished sliver and black. Size: Unit 
14±* x 12* w x W. Speakers 14*" x B" x Si". 



CARTRIDGES (p. & p. 12rp.) 

GOLDRING G850 £4.20 

GOLDRING G800 £8.90 

GOLDRING G8O0E £11 00 

GOLDRING G800 super E £16-00 

SONOTONE 9TAHC £2-35 

SHUREMSd £4-95 

SHURE M445/7/C £7-20 

SHUREM55 £9-20 

SHUREM75E/11 £15-00 

We have the complete SHURE range In stock. 

SCOOP BUY 

SMC-101 MOVIN6 MAGNET STEREO 

CARTRIDGE. 

PRICE: £3 -25. 

MCI-3 HIGH FID ELIT Y STEREO 
MOVING MAGNET CARTRIDGE. 
PRICE: £8-00. 

For complete specification on the above tee 
our March issue, Page 889. 

SPECIAL OFFERS 
SPEAKERS 

Wharfedale — Denton — Triton — Melton — 
STE — MA. 

Full range in stock at UP TO 50% DIS- 
COUNT FOR PERSONAL CALLERS 
ONLY. 

HEADPHONES 

For 1 month only we offer 25% OFF list price 
of all KOSS models. 

Example: PR04AA. List price £23-00. 
OUR PRICE £21 -00 plus 37p p. A p. 

SAVE OVER 30% ON A COMPLETE 
SYSTEM 

List Price 

GARRARD SP 25 MK III £16-45 

PLINTH AND COVER £6-00 

G800 CARTRIDGE £13-00 

HL AUDIO SA 707 £27-00 

2 APOLLO 8 SPEAKERS £27-50 

OUR PRICE £56 -94 + £2 -50p. p. & p. 



MANY OTHER BARGAINS IN STOCK 
FOR PERSONAL CALLERS DURING 
WEEK. 



WHY PAY MORE— APOLLO 3-WAY SPEAKER SYSTEMS 

The Systems are housed In handsome Slim-Line Cabinets of Modern Design, finished in Polished Teak with 
Padded Front Panel covered In J.C.I. Vynalr Grille. 

The APOLLO 3- WAY SPEAKER SYSTEMS are designed and Crossover Network. Specification: Impedance 

built on the Infinite Baffle Principle and are completely Airtight 4-8 ohms (15-16 ohmato order). Power Hand- 

and fully padded to damp out any Panel Resonance. Polished on 

all sides they can be used either vertically or horizontally and are 

ideal for Shelf or Wall Mounting. 

Below are Just a few from the APOLLO comprehensive range 

starting with: 

APOLLO- 15 3- WAY SPEAKER SYSTEM 

Impedance 8 ohms. Power Handling 15 watts. RMS (30 watts peak). 
Frequency Range: 35 to 18,000Hz. Colour; Teak. Size 21 x15x7lln. 
PRICE £18 -50 each (p. & p. £1 -00) . 

THE APOLLO-10 3-WAY SPEAKER SYSTEM employs a 
specially designed loin. Baas Unit which has a high efficiency 
Anisotropic Ferrite Magnet and two 41 n. Treble Unite and LC 



ling 10 watts RMS (20 watts peak). Frequency 
Range 50 Hz to 18,000 Hz. Size 21 x Hi x Of. 
Finish-. Polished Teak. 
OUR PRICE £13,47 each (65p. p. A p.). 

APOLLO-8 3-WAY SPEAKER SYSTEM 

As above but 7 watts RMS (14 watts peak). 
F.R. 55 to 18,000 Hz. Size 20 x 12 x Sin. 
£10-12 each (50p p. i. p.). 

APOLLO-66 3-WAY SPEAKER SYSTEM 

As above but 5 watts RMS (10 watts peak). 
F.R. 75 to 18,000 Hz. Size 141 x 8 x Bin, 
PRICE £0.97 each (37rp p. 4. p.). 



PERSONAL CALLERS WEL- 
COME, We are always available to 
advise on the best system to tult 
your need and pocket. 



OUR OWN CAR PARK (at rear) 

You have no parking problems when 
you pay us a visit. 



UNBEATABLE VALUE 

The largest and best quality range 
ol stock at LOWEST POSSIBLE 
PRICES is usually available. 



The prices shown are current at the 

time of going to press but ara liable 
to alteration. They supercede any 
previous offer. 



Send Postal Orders, Monty Orders, Cheques, etc. to 



For Information only send stamped addressed envelope 



AUDIO SUPPLIES 



AUDIO SUPPLIES (PW4) so Stamford hill london, n.16 (The a.io) 

Tel: 01-806 361 1 



Open 9.30 a.m.-t p.m. Monday to Saturdays, EASY TO FIND. 50 yards from 
(B. R.) Stoke Newlngton Station. 87, 149, 247, TO, 243 Bum* pass our door 
: Personal call «« please note that cheques are only accepted If accompanied by a bank cheque card. (HOTE: NOT BARCLAY CARDS) 



987 



The Gen 



988 




Adler Story 



Once upon a time Gerry Adler 
worked a 25 hour day making and selling 
valve filament testers. And very efficient 
they were too. 

But at that time the Japanese could 
make them for about half the price, and 
sent Gerry one to prove it. It was as good 
as the ones he was making, so he sold it. 
And every other one he could get into 
the country. 

After a time Gerry decided to go 
one step further. He designed some 
electronic equipment and had it built to 
his specification in Japan.Then he sold it 
here under the brand name 'Eagle*. 
Nothing particularly remarkable about 
that. But Gerry couldn't stand the idea 
of a barrier between him and his 
manufacturers. So he went to Japan. He 
poked„his nose into all the electronics 
factories to find out how the Japanese 
worked.And when he got back he started 
to learn Japanese, and to study their 
history, culture and way of life.That way 
he had fewer communication problems 
and could get what he wanted. 

That's what matters to Gerry. He's 
very fussy about what goes out under the 
Eagle banner. Because Eagle aren't in the 
filament testing business any more. They 
make just about everything electronic: 
amplifiers, test equipment, PA systems, 
intercoms, old uncle substation and all. 
Eagle is now twelve years old, and has 
opened offices in New York, Tokyo and 
Brussels. 

This isn't just so much chest 
expansion on Gerry's part. He puts his 
money where his mouth is. If you think 
one of his products is not as good as a 
rival's, or it's faulty, or it's not all it 
should be, Gerry wants to know. 

So write to him personally. Hell 
do something about it. He wants to make 
sure the Gerry Adler story has a happy 
ending. 

Eagle International 

we don't stand still. 

Coptic Street, London WC1A 1NR. 
Telephone 01-636 0961 



989 




l^kW FAN HEATER 

Three poaition inrltcbinf? to 
suit changes in the weather. 
Switch up for full heater (2i 
kW), switch down lor half 
heat (l|kW), switch central 
blows cnld jar summer cooling 

- adjustable Itunnastot sets 

a*anto control and eaiety cot- 
nut. Omplete kit 13-75. 
t'osl and ins. 38p. 

II VOLT BATTERY CHARGER 

Xade in Japan, this ia Wry small ami neat. 
Regular use will keep your car battery in good 
Irip throuKhout tile winter. Silly prire £1-85 
plos 23p pOHtage and in™ ranee. 



QUICK CUPPA 

Mini immersion Healer, 3a£l« 
!M0/240v. Bolls lull crop in about 
two tiilcuten. Use any socket or 
lamp holder. Have at nedsut' 
lor tes, baby's fowl, etc. £1 86, post 
and Insurance 14p. ISv. ear tinhIcI 
also available £1. 

PLINTH AND COVER 

Suitable lor moat auto 
changers, teak base with 
tinted perspe* cover £4-Sh 
pluu S3p postage. 

THYRISTOR LIGHT 
DIMMERS 

"Will dim incandescent lighting 
up to 600 watts from full 
brilliance to out. Assembled anil 
win-il ready to install £3. 



AUTO ELECTRIC CAR AERIAL 

"With dash board control switch — fully 
extendable to 40" or fully retracted 
Suitable lor I2V positive or Neg. 
earth supplied complete with 
fitting instruction!! and ready 
wired dash board switch £5 96 
plus '-Tip. p. & p. 

COMPUTER TAPE 

'2,400 It. of the best magnetic 
tape money can buy. Hade by 
E.H.I., lln. wide almost un- 
breakable arid on a H.'im metal 
computer spool. Users have 
claimed successful results with video as 
sound recordings {I plus 33p post. 
CasHctte to hold .ipool 50p eitra. 






HORSTMANN -'TIME AND SET" SWITCH' 

i K in amp Switch). Just the thing it you want to come tome 
to a warm house without it costing you a fortune. Hot; can 
delav the switch on time oi your electric fttej. etc. tp W 
14 hours from setting time or you can use I be twitch to mve 
a boost period of up ta 3 hours. Equally suitable to en n rid 
processing. Regular price probably a rami 4 fe> Specs*! *n>P 
price SI B0, p. ft in". 28p. 



I HOUR MINUTE TIMER 

Made by famous Smiths company, these have a Inure 
clear dial, size 41 * 3), which can be net in niinule» up 
to I hour. After itrewst period the bell rings. Ideal tor 
processing, a memory jogger or. by adding simple lever, 
would operate micro -switch (1-15. 

STEREO SIX 

The amplifier 

sensation of thit year 

You will be amazed a; the 

fullness d! reproduction and at 

the added qualities your records 

or tuner will reproduce. Built 

Into metal cabinet elerantly 

styled in simulated teak finished 

furnishings, this aiuplifttr unes 

.unrated (solid etate circuit with an output power of 6 watts R.M.H. split 

,,ver the two channels. Tlie amplifier is ideal for use with normal pick-nos and 

lunere, it bas a double wound main* transformer and ganged volume and tone 

ontrola — also switching for Mono to Stereo, tuner or pick-up. Other c jntrnls 

iinclnile -treble lift and cut", "balance" and separate mains on,'otI twitcb. 

I NUEPEATABLE PRICE is 49 plus 38p post and insurance. 

STANDARD WAFER SWITCHES 

Standard Size 1J wafer — silver-plated j amp 
contact, (standard |" spindle -2". long— with locking 
washer and nut. 





S((. (i 
Pol - 



in 



!■_> 



1 pole 
'2 poles 

3 poles 

4 poles 

5 poles 
poles 
7 poles 

6 poles 
poles 

10 poles 

11 poles 

12 poles 



33ji 33p 
33p S3p 



33p 

33p 33p 



313 j: 

33p 

33p 33p 



33p 

33 p 6 tip 



33p 

33p 55ii 



56p S6p 
Ofip 



66p 

55p 



S5p 6Jp 
66p 55p 



55p 55p 

76p 



33p 
5Sp 
Gap 
S6p 
75 p 
7Sp 



33p 
33p 
65p 
5Sp 
75p 
75p 
95p 
Sop 



Up 

5Sp 



Top 
75p 



75p 7Sp 



75p £11S 

Sop £115 

95 p £135 

95p £135 



33p 
33p 
55p 
Sop 
75 p 
75» 
95p 
95p 
£115 
£1X5 
£135 
£135 



33p 

33p 
55p 
55p 
75p 
75p 
S5p 
S5p 
£115 
£115 
£1 35 
£135 



33p 33p 
55p 55p 

75p 75p 
95p 9Sp 
£115 £1 15 
£135 £1 35 
£1 55 £1-55 
£1-75 £1 76 
£1.95 £1 95 
£8-15 £815 
££35 £8 35 
£855 £2-55 





SPARTAN Portable 
RADIO 

Long and medium wave. 

7 transistor, size Gin.x 

4ln, Xljin. with larger 

than usual speaker giving 

very good tone. Built-in 

ferrite aerial and tele- 

Hcopic aerial for distant 

stations. A real bargain 

complete with leather case, carry sling. rar|diK 

and cane £3-75 pi as 2jp post and In*. 

MULTI-SPEED MOTOR & 

lieplac-mient In many well 

known food mixers. Six speeds 

are available. B00. 850 and 1100 

r.p.m, irom either or both of the 

nylon sockets (Where the beaters 

of the food mixers normally go I 

and 8.000. l'i.000 and 15,900 

r.p.m. (ideal polishing speeds) lrom die main dri-n- 

shaft, Verv powerful and useful motor size appoi. 

i\o. diameter, 5 in. long. Price 90p plus 23p, 

p. * ins, J-j or more post free. 

MAINS OPERATED CONTACTOR 

220/ 240 v. 50 cycle solenoid 
with laminated core so very 
silent In operation. Closes 4 
circuits each rated at 10 arops- 
Extreroely well made by a 
(lerman Electrical Company. 
Overall siic a J x 3 x. 2i». 
£1 each. 



DOUBLE ENDED MAINS MOTOR 

On feel with holes lor screw- 
down fixing. To drive models, 
oven, blower heater, etc. 50p 
each, plus 18p port and 
insurance, 6 or more post 
tree. 

O.OOSmFd TUNING 
CONDENSER 

Proved design, ideal for straight K 
reflex cin-uirs 13p nrk, £120 *w 





Where postage is not stated then orders 
over £3 are post free. Below £5 add yop 
Beml-conductom add 5p post. Over £t 
post free, S.A.E. wrth enquiries please- 



ELECTRONICS (CROYDON) LTD 

Dept PW £66 London Road, Croydon CRO-2TH 

Alio IOT/J Tamworth Road, Croydon 



RSGB BOOKS FOR YOU 



AMATEUR RADIO CALL BOOK 

1971 edition 
Includes details of new callsigns issued by MPT up to 
31 August 1970, and more than 2,100 changes of 
address compared with the 1970 edition, 128 pages, 
Including 14 pages of valuable supplementary infor- 
mation. 52p post paid 

AMATEUR RADIO TECHNIQUES 

By Pat Hawker, G3VA 
Third edition. A source of many useful circuits and 
aerials incorporating the latest amateur techniques. 
Contains 208 pages and nearly 500 diagrams. 

£1.13 post paid 

A GUIDE TO AMATEUR RADIO 

By Pat Hawker, G3VA 
Fourteenth edition. 100 pages. 

The latest edition of this indispensable aid to all who 
want to know more about amateur radio. Designed to 
assist the newcomer to this unique hobby. 
Revised and expanded. 47p post paid 



These are three of a complete range of technical 
publications, log books and maps, all obtainable from : 

RADIO SOCIETY of GREAT BRITAIN 

35 DOUGHTY STREET, LONDON, WC1N 2AE 



FMTASrtC M*GAIH OfH*! 



TRAIMSEUROPEAIM 



Transistorised Stereophonic High Fidelity 
AM FM Tuner Amplifier System, 



O 



This system includes tlie; elegantly styted solid stare Teak finished cabinet 
tuner/amplifier. Co'-ering VHf/FM, Medium and long wavebands. The 
latest 4 Speed 8S.lt. Mono/Stereo record changer with 7-IOin. x 6in. 



....itching e1liptL_ 
at less than half 



ipcalterf. A complete 
Tor ma I price. 



Hi-Fi Stereo Radiogram 

SPECIAL OFFER 



Easily fitted no technical 
knowledge necessary. 

Credit Terms avail, 
able. First montHy 
payment of £5 33 fol- 
lowed by 9 monthly 
payments of €A ?S. 
Total Credit Sale Price 
£49 SO. Send £5 83 today. 

FABULOUS VALUE 

Transistorised Stereo Hi-Fi Record Player 

Build your own h i-Fi Record Player with the Serenade folTf^ran 

siscorised amplifier which comes complete with 1- lOin. x 6in. 

speakers and the latest 4 Speed B5R Speed SterecWMono Record 

Changer. 

Credit terms 1st monthly payment £4>J6 Col- 
& P. lowed by 9 monthly payments of £3-38 (Total 

** 88b ciS price £33-08). Send £4-26 today. 

EASY TO INSTALL HO TECHNICAL KNOWLEDGE REQUIRED. 

■ B| CALLERS WELCOMEH M ■■ 
PL'£ASE SEND ME FREE DETAILS OF YOUR RANGE 

Karoe 

ddress W* 




£30 



Post coupon 
NOW for... 

FRHl 

leaflets) 



100, Chase Side London N.M 
Tel: 01 -886 3733/9666 



990 



ELECTRIC CLOCK 
WITH 25 AMP SWITCH: 

Made by Smith's, thenr units are j 

OS fitted to many top quality ] 

cookers to control the oven. The 

clock [a mains driven nnd fr?- I 

quency controlled so it is i 

trerjiely accurate. The tico ama.! | 

dials enable switch on and 

times to be accurately 8«t. Ideal __^ 

for Bwitchirifi on tape record ere* Offered at only a 

fraction of the regular price — new ami u-jiiHed. 

only £2, le.in than the value of the clock alone — 

post and in sura »ee 14p. 




FLUORESCENT CONTROL KITS 

Each kit comprises seven items — Choke, 2 
tube ends, starter, starter holder and 2 tube 
clips, with wiring Instructions. Suitable lor 
normal flu orescent tubed or the new "Grolux" 
tabes lor flsh tanks and Indoor plants. Chokes 
are super*Allent, mostlv resin tilled Kit A 
—10-20 w. £1 Kit li— 30-40 w. II Kit 
C— SO w. £180. Kit K-tlfl w. £1-20. Kit IT 
tor Sit. 125 w. tube £1-75. Kit Mr'i Is tor 
Sin., Uin. and 12iu. miniature tubes £1. 
Kit MF2 tor 21m. 13 w. miniature tube £1. 
Postage on Kits A and B 23p for one or two 
kite then 23p for each two kits ordered. 
Kits C, D and E 23p on first kit then 18p 
for each kit ordered. Kit P 33p then '23 p for 
each kit ordered. Kit MF1 18p on first kit 
then ]5p on each two kits ordered. 



BLANKET SWITCH 

Double pole with neon let 
Into side no luminous in dark, 
Ideal for dark room light or for 
use with waterproof element, 
plastic case 30p each. 3 heat model 40p 




BLANKET SIMMERSTAT 

Although looking like, and fitted as an 
ordinary blanket switch, this is iii fact a 
device for switching on for varying time 
periods, thus giving a complete control 
from oH to full heat. Although suitable for 
controlling the temperature of any other 
appliance* using up to 1 amp. Listed at 
4T40 each we offer these while our stocks 
last at only 85p. each. 



— j -j,- ^ — REED SWITCHES 

Class encased, s witches operated by external 
magnet — gold welded contacts. We can now oHer 
3 types: 

Miniature, II"- long * approximately T tn. 
diameter. Will make and break up to i A up to 
300 volts. Price 13p each. £1B0 dozen. 
Standard. '2 In long x 3f Win. diameter. This will 
break currents of up to 1A, voltages up to 200 
volte. Price I Op each. 90p per dozen. 
Flat, Flat type, Sin. long. Just over l/Wln. thick, 
ap proximately J In. wide. The Standard Type 
flattened oat, so that it can be fitted into a smaller 
space or a larger quantity may be packed Into a 
square solenoid. Rating 1 amp 200 volts. Price 
30p each. £3 per dozen. 

Small ceramic magnets to operate these reed 
.i witches 9p each. BOp per dozen. 

HIGH CAPACITY ELECTROLYTICS 
Brand new, not ex-equlpment. 
100 mf.d 2Sv„ op each. BOp do:. 
280 mid. 50v., IBp each. £1 95 doz. 
400 mfd. 40v., 22p each. ££30 doz. 
500 mfd. 12v., lOp each. £1 06 doz. 
500 mfd. 25v., IBp each, £1 80 doz. 
500 mfd, 50v„ 23p each. £2 40 doz. 
500 mfd. 350v,, 4Sp each. £4 50 doz. 
I00O mfd. 12v., 15p each. £1 SO doz. 
1000 mid. ISv ., 17p each, £1-70 doz. 
1000 mfd. 64v„ 37p each. £4 doz. 
■2000 mid. 25v.. 84n each. £3 05 doz. 
5000 mfd. 12v„ 24p each. (2-40 doz. 
10,000 mfd, fir,, 29p each. £3 doz. 
10,000 mfd. 15v., 43b each. £460 doz. 
15,000 mfd. 10v„ 58p each. £5 doz. 
60,000 mid. 8 v., £110 each. CIO doz. 
70.000 mfd, 18v., £2 each. ISO doz. 
S amp ISv Battery Charger Kit — comprising 230/40 
mains transformer with 3 amp secondary and 3 amp 
rectifier £116 plus 23p post. 

18 volt 1,? amp Power Piek. This comprises 
double-wound 230/240 V mains transformer with 
full wave rectifier and 2000 m/f/d/smootbing. 
Price a-W. 

Sonotone Stereo Cartidge. Turnover type. ref. No' 

19 Tl. This fits most British pick-ups and is a 
really excellent reproducer. Limited quantity, £1. 
5 amp 3 pin Sockets. These are always good stock, 
you never know when you will need some. Famous 
make, brown bakelite, standard size, 12 for 85p 
plus 23p post. 

Ditto hat with switch. 12 for £1 plus 23p post. 
IS amp lockets, flash mounting. Bakelite. cream, 
less switch, 6 for £1. 

Bakelite Panels, many thicknesses. We have just 
taken delivery of approximately 10 tons of bakelite 
In varying thicknesses from 2 In. to a few thou. 
If you have a need for any of this then we would 
be glad to supply. The thickest Is very heavy and 
could be used, for instance, as a bed for a motorised 
unit. Medium thickness is useful lor lront panels 
of instrument, etc., etc. Cut to your size price is 
SOp per lb. plus 30p cutting charge plus carriage. 
2 amp 3 pin Switched sockets for surface mounting, 
brown bakelite. Made by famous maker. 18p each 
or £1-20 dozen. 

100 Ajaorted Silicon Kecti fieri O.P. and (witching 
closes. Small and very small sizes. A real snip lor 
experimenters. 65p per 100. 



20 AMP ELECTRICAL, PROGRAMMER 

Learn In your sleep: Have Badio playing and kettle 

Imiling as you awake — switch-on lights to ward off 

intruners — have warm house to come home to. All 

these and many other things you can do tl you invest 

in an Electrical Programmer, Made by the famous 

Smiths Instrument Company. This Is essentially a 

230/240 volt mains operated Clock and a 20 amp Switch, the switch-off time of 

which can be delayed up to 12 hours (continuously variable not stepped). 

Similarly the switch-on time can be delayed. This is a beautiful unit, size 5} x 

3 1 x 2 Jin, deep. Metal encased, glass fronted with chrome surround. Offered 

at (2.40 plus 23p postage and Insurance. 




HI-FI SPEAKERS (15. 30. 40 & 100W) 

FULL FT12 INCH LOUDSPEAKER. This Is undoubtedly 

one of the finest loudspeakers that we have ever offered, i 

produced by one of the country's most famous makers, it J 

has a die-cast metal frame and is strongly recommended 

for Hi-Pi load and Bhvthm Guitar and public address. 

Flux JDensity 11,000 gauss—Total Flux 44.000 Maxwells-- 

Power Handling 15 watts R.M.8. Cone Moulded flbre- 

i'r-.|. r»spon«,- ::ii- 10,1.100 :m..-. — Specify 3 or 15 ohms 

Mains resonance 60 c.p.s.— Chassis Diam. 12in. — 12Jln. 

over mounting tugs— Raffle hole 11 in. Diam. — Mounting 

holes 4, holea— Jin. diam. on pitch circle lljin. diam. — Overall neight oiin. 

A £6 speaker offered for only £4 plus 37p p. * p. 12in. 40 watt £7 cair, 43p. 

IS In. 25 watt 28 carr. 53 p. Win. 100 watt £18 50 carr, £1-50. 



HP 



INTEGRATED CIRCUIT BARGAIN 

A parcel of Integrated circuits made by the famous Flessey Company. A 
once-in-a-llfetlroe offer of Micro-electronic devices well below cost of manu- 
facture. The parcel contains 5 ICs all new and perfect, first-grade device, 
definitely not sub-standard or seconds. 4 of the ICs are single silicon chip 
GP amplifiers. The 5th Is a monolithic NPN" matched pair. Regular price 
of parcel well over £5. Full circuit details of the ICs are included and in 
addition you will receive a list of many different ICs available at bargain 
prices 5/- upwardB with circuits and technical data of each. Complete parcel 
only £1 post paid. BO.VT MISS TBIS TESSIPIC BARGAIN. 



THIS MONTH'S SNIP 




24-HOUR ELECTRIC TIME SWITCH 

Made by Smiths, these are AC mains operated, 
SOT CLOCKWORK. Ideal [or mounting on rack 
or shelf or can be built Into box with 13A socket. 
2 completely adjustable time periods per 24 
hours, 5 amp changeover contacts will switch 
circuit on or off during these periods. £2 60 post 
and Ins. 23p. Additional time contacts SOp pair 



DISTRIBUTION PANELS 

Just what you need for work bench or lab. 

4 x 13 amp sockets in metal box to take 

standard 13 amp fused plugs and on/off switch with neon warning light. Suppled 

complete with 7 feet of heavy cable. Wires] up ready to work, £2 less plug 

£2 25 with fitted 13 amp plug; £2 40 with fitted 15 amp plug, plus 23p P. 4 I. 



, BARGAI N OF THE YEAR 



MICROSONIC KEYCHAIN RADIO 

7 transistor Key chain Badio in very pretty 

case, size 2| x 2$ x ljln. — complete with eoft^ 

leather zipped bag. Specification:— 

Circuit: 7 transistor superheterodyne.] 

Frequency range: 530 to 1600 Ke/s. Sens!-' 

tlvity: 5 mv/m. Intermediate frequency: 

465 Ke/s or 455 Kc's, Power output: 

40m W, Antenna: ierrite rod. Loudspeaker: 

Permanent magnet type. 

In transit from the East these sets suffered 

slight corrosion as the batteries were left In 

them but when this corrosion Is cleared away they 

should work perfectly — offered without guarantee 

except that they are new. Prk* only £1-25 less batteries plus 13p. 

6 for £7 post free. Fair ol rechargeable batteries and charger 8Sp. 





4 AMP VARIAC CONTROLLERS 

With this you can vary the voltage applied to your circuit from 
zero to fall mains without generating undue beat. One obvious 
application therefore is to d im I ight ing. Ex equipment hut little 
used — as good as new offered at approx. half price. £6 plus 
75p. post and ins. 



19 PIECE 50CKET SETS 

Complete with wall or bench rack. Most useful sizes 
from i' to {j * BOp plus 23p post and insurance. 



HONEYWELL PROGRAMMER 

This is a drum type timing device, the 
drum being calibrated in equal divisions 
for switch setting purposes with trips 
which are infinitely adjustable lor position. 
They are also arranged to allow 2 opera- 
tions per switch per rotation. There are 15 
changeover micro switches each of 10 amp 
type operated by the trips thus 15 circuits may 
be changed per revolution. Drive motor is 
niains operated 5 revs per mm. Some of the many 
uses of this timer are Machinery control, Bailer firing. Dispensing amfVending 
machines, Display lighting animated and signs, S ignalling, etc. Price from makers 
probably over £10 each. Special snip price £S.7S plus 25p post and insurance. 
Don't miss this terrific bargain. 



Mains Connector 

A quick way to connect 
equipment to the mains 
safely and firmly — L, 8f. 
and E. coded to new 
colour scheme: discon- 
nection by plugs prevents 
accidental switching on: 
has sockets which allow 
Insertion of meter without disconnection: cable 
inlets firmly hold one hair wire on up to four 

7.020 cables. 65 p each. 




CONTROL 
DRILL 

SPEEDS 





DRILL 
CONTROLLER 

Electronically changes 
Hpeetl from approxi- 
mately 10 revs, to 
maximum. Full power at 
all speeds by finger-tip 
control. Kit includes all 
parts, case, everything and 
full instructions. £1-60 plus 
13p pout and insurance. 
Made up model also avail- 
able, {100 plus 13p post A p. 



BALANCED ARMATURE UBJT , 
S00 ohm. operates speaker or micro- ^^b^ 
phone, so useful in Intercom or similarjKC'i) 
circuits. 33p ea. £5.30 doz. " ^J _, 

-> 

PROTECT VALUABLE DEVICES 

FROM THERMAL 
RUNAWAY OB 
OVER - HEATING: 
Tnyristors, rectifiers, 
transistors, etc.. 
which use heat- 
sinks can easily be 
protected. Simply 
make the contact 
thermostat part of 
the heat sink. 
Motors and equip- 
ment generally, can also be adequately protected 
by having thermostats in strategic spots on the 
casing. Our contact thermostat has a calibrated 
dial for setting between SOdeg. to 190 deg. P. or 
with the dial removed range setting is between 
SO to gOOdetv.E,. Price SOp. 

THERMOSTAT 
WITH PROBE 

This has a sensor 
attached to a 15A 
switch by a 14in. 
length ol flexible 
capillary tubing 
— control range Is 
, 20° F to 150*F so 
is suitable to control soil heating and liquid 
heating especially when in buckets or portable 
vessels as the sensor can be raised out and lowered 
into the vessel. This thermostat could also be used 
to sound a bell or other alarm when critical temp. 
Is reached in stack or heap subject to spontaneous 
combustion or If liquid is being heated by gas or 
other means not controllable by the switch. Made 
by the famous Teddlngton Co., we offer these at 
63p each. Postage and insurance 14p. 



MAINS MOTOR 

Precision made — as 
used In record decks 
and tape recorders — 
Ideal also for extractor 
fan. blower, heatera, 
etc. New and perfect. 
Snip at SOp. Postage 
15p for firat one then 
5p for each one 
ordered. 



NEED A SPECIAL SWITCH? 
Double Leaf Contact. Very slight pressure closes 
both contacts, ftp 
= each, (Op doz. Plastic push- 
rod suitable for operating, 
'-' f I 5p each, 45p doz. 



MINIATURE 
WAFER SWITCHES 

2 pole, 2 way — 4 pole, 2 way— 

3 pole, 3 way — 4 pole, 3 way — 3 
pole, 4 way — 3 pole. 4 wav — 2 pole 
B way— I pole, 12 way. All at 18a 
each. £1 80 dozen, your assortment. 





WATERPROOF HEATINK 

ELEMENT 
26 yards length TOW. Self-regulating 
temperature control. SOp post free. 



MICRO SWITCH 



S amp. changeover contacts, 9p 
each, £1 doz, 15 amp. Model 
lOp each or £105 doz. 



Where postage is not stated then orders 
over £5 are post free. Below £5 add BOp. 
Semi-conductors add op post. Over £1 post 
free. S.A.E. with enquiries please. 



ELECTRONICS (CROYDON) LTD 

Dept. PW, 266 London Rd., Croydon CR0 2TH 

Also 102/3 Tamworth Road, Croydon 



991 



Traiii for tomorrow's world in 
Radio and Television at The 
Pembridge College of Electronics 



Your first day on Television: 
21st April 1971 

This is your opportunity to train 

as a television and radio 

engineer on our full-time 

2 year College Diploma Course. 

That is the way to get into a 

rapidly growing industry with 

a tremendous demand for 

skilled technicians. You will be 

given theoretical and practical 

nstruction on colour 

television receivers, following a 

syllabus specially designed 

to cover the new City and 

Guilds Radio, Television 

and Electronic 

Technicians' Course. 

Minimum entrance 

requirements are Senior 

Cambridge or '0' Level, 

or equivalent in 

Mathematics and 

English. 

Complete the coupon 

below and we will 

send you the details 

about training for 

an exciting, new 

career. 




To; The Pembridge College of A 
Electronics, (Dept. pwi }, 
34a Hereford Road, London, 
W2 5AJ. 

Please send, without obligation, details 
of the Full-time Course in Radio, 
Television and Electronics. 



NAME 
ADDRESS 




M. I B. COMPONENTS (LEEDS) LTD. 

(INCORPORATING M. & B. RADIO) 

38 BRIDGE END, LEEiDS 1 Telephone 0532-35649 

geiger counter:; 

Well-known contamina- 
tion meter comprised cf 
main unit fitted with 
meter marked in 'Milli 
Ron tg ens/Hour", probe, 
lead and carrying case. 
A very sensitive set which 
will give a good reading 
from most pocket 
watches. Very low battery 
consumption. Audio out- 
put available from socket 
on front panel. Supplied 
in new or as new 
condition. 

Model 1. Supplied witf. internal vibrator power supply unk. enabling 
sei to work from 4 pen ;ell batteries £4'47J- plus 37tP- p.p. 
Model 2. Requires 2 HT batteries (not included) £3-75 plus 37 rp p.p. 
TRANSISTOR MODtLATOR FRONT END 4 transistor modulator 
pre-amp panel 2J"x+8". Fitted with preset microphone gain control 
and mod. filter. Originally used to drive an NKT404 which drove a pair 
of NKT404s. Supplied brand new with circuit of complete modulator 
£M2J plus 7ip p.p. 

TRANSISTOR INVERTERS, Both models are brand new. 
Model 1. 12 vdc input 270 vdc at ISQmA approx. output. £3-25 plus 
20p P.P. 

Model 2. 12 vdc input 330 vtlc at 330mA approx output. £5'7S plus 
25p p.p. 

VHF RECEIVER UNIT TYPE R1933A. 18 miniature valve vhf receiver 
ideal for 2 metres, 4 metres or aircraft band. Requires p.s.u. and 
oscillator. £2-25 plus Kts p.p. 

300 UNTESTED UNMARKED TRANSISTORS. £1 00 plus lOpp.p. 
600 UNTESTED UNMARKED DIODES. £1 00 plus lOp p.p. 
ELECTRO MAGNETIC COUNTERS. 4 digit GPO type counters. 
Used but tested. Six for £1-30 plus 3/6d. p.p. 

DESK TELEPHONES. GPO type desk telephones complete with dials. 
Used but tested. Two for £1-624- plus 374p p.p. Four for £3 00 plus 
50p p.p. 

CONSTRUCTOR'S PARCEL NO. 1. Contains one 455Kc/s transistor 
FM IF panel, new but faulty: 60 untested unmarked diodes: 3 audio osc 
and timer I/Cs with (ircuils: 6 miniature 12 vdc lOOjtF capacitors: 
4 matched diodes: 5 253010 and 5 DT1602s. £1-874 post free. 
Send for lists of other parcels. 

We also have in stock tiany other items of general interest. 
Please send s.a.e. for o it latest lists. 



BAKER I2in. REGENT 

An inaxpeniive unit for the beginner in 
high fidelity >nd (or general purpoxi. May 
be u>ed to advantage with any Radio, 
Amplifier or Television receiver. 
Maximum Power 15 watt* 
Sin fteso nance 45 c.p.f . 

Flux Deniity 12, i>QQ gauii 
Voice Coil impedance 

J or 8 or IS ohm model ■ 
Utaful responte 

45-l3,XWc.p.t, 
Nett weight S lb*. 

GUITAR MODEL 'GROUP 25 
rating £7 
Latest catalogue I/- with tncloiure plant 




POST 
FREE 

' 25 watt 



Baker Reproducers Ltd 



Benjham Manor Road Passage, Thornton H«ath, Surrey. 01-684-1665 



When in LUTON, BEDS, you must visit the . . . 
SELF-SERVICE RADIO COMPONENTS SHOP 



Serve yourself from a selection of 1,200 boxes 
of Manufacturer's surplus stocks and save money. 

|9 a.m. to 5.30 p.m. every day. 
Clcsed all day Wednesday. 

SURPLECTRONICS 

216 LE/ GRAVE ROAD, LUTON, BEDS 



992 



Which ever way you choose 






(BUILT OR KIT) 




MARTIN AUDIOKITS 

For the do-it-yourself enthusiast, the return of a 
great range of hi-fi modules 



You are going to enjoy 

better listening for 

less cost and greater reliability 



ready to play 




LEWIS AUDIO SYSTEMS comprise ready built equipment 
designed and built to advanced technical standards of efficiency 
and styling. Their prices make true hi-fi available to a wider public 
than even Based on the excellent Lewis Audio SA. 55 stereo 
amplifier In which FETS are used In the pre-amp to ensure better 
quality throughout, the range offers choice of free-standing ampli- 
fier with separate playing unit in plinth with plastic hard top or the 
Compact assembly in which the amplifier is built info the base of 
the plinth and motor assembly. Separate matched speakers are 
available for either system. Illustrated above is the Lewis S.55 Mk. II 
Compact System. 

LEWIS AUDIO SYSTEMS 



SA.SS STEREO AMPLIFIER-6 watts 
RMS output perch. Into 15 ohm speakers 
Controls — Input seleclor/Vol/Bass/ 
Treble/Balance/ On-Off. Tape Record 
and replay faculties. DIN socket connec- 
tions. Modern teak finished cabinet. 

R.R.P £11-90 



PLINTHS WITH HARD TOPS A 
FITTED GARRARD UNITS 

Garrard 2025TC with Sortotone 9TA.IHC 
R.R.P. £16-50 

Garrard 408 wtth Sonotone 9TA/HC 

R.R.P. £M-1« 

Garrard SP.25 Mk. Ill leas cartridge 

R.R.P. £»•« 



SC.S5 MK. II 'Compact' with Garrard 
2025TC and SA.55 amplifier built into 
plinth R.R.P. £«■» 



LOUDSPEAKERS 

LS. 16 'MaiOf'— 13" x 6' three way 
sy*tem In American Walnut finished 
cabinet, 8 ohms R.R.P. £1t*7» 

LS.17 6" three way system In teak or Am. 
walnut finish. 15 or B ohms 

R.R.P. £10M 

LS.18 8* three way system In teak 
or Am. walnut finish 15 or 8 ohms. 

R.R.P. £12-M 



for the constructor 

MARTIN AUDIOKITS were first to make modular unit construc- 
tion available to the hi-fi enthusiast keen to save by building his 
own assembly. AUDIOKITS were first to feature "add-on-ability" 
by which a simple system could be expanded to high performance 
stereo equipment by the addition of easily added on units. Many 
who built with MARTIN AUDIOKITS years ago continue to enjoy 
unsurpassed quality and reliability from them to this day. NOW 
YOU CAN BUY AUDIOKITS AGAIN to allow you to build a 
high fidelity system to your personal choice and which will satisfy 
completely on performance, simplicity of assembly, robustness and 
reliability. These units are beautifully engineered and solidly built 
for a lifetime of trouble-free service. You can start with mono and 
add on units to make stereo, or build with stereo throughout. 

TYPICAL MARTIN ASSEMBLIES 

1478E Five stage matched Input selector unit; controls and pre-amp; power amp. 

(10 watts RMS into 15 ohms) power supply; front escutcheon plate (mono) 

Total price £17*S* 
1478SE Similar to above but for stereo. Total price £21*5 

9748SE Stereo assembly for use with high grade ceramic and low power mag. 

pick-ups. Total price £»•>» 

All units are obtainable separately , State pick-up when ordering. 

• EACH MARTIN AUDIOKIT 
MODULE IS COMPLETE IN 
[TSELF AND REQUIRES THE 
ADDITION OF NO FURTHER 
COMPONENTS TO IT. 

«) ALL UNITS INDIVIDUALLY 
TESTED AND CHECKED BE- 
FORE LEAVING OUR FACTORY. 




• TRADE ENQUIRIES WELCOME 



Coupon bring;* information 



TO LOUIS & LEWIS (ELECTRONICS) LTD. 154 HIGH ST 
I BRENTFORD, MIDDX. 

I am particularly interested in MARTIN AUDIOKITS 

Please send details, {post free) to: LEWIS AUDIO SYSTEMS 



LOUIS & LEWIS 



(ELECTRONICS) 



LTD 



NAME 



154-155, HIGH STREET, BRENTFORD, MIDDLESEX 

Telephone 01-560 1181 



ADDRESS 

I 



PW.1 



993 



As! pad ORION 



22^ 



THE WORLD'S SMALLEST 
TWO WAVEBAND, 6 
TRANSISTOR RADIO 

Music, new?, sport, wherever you are. 
7-day money back guarantee if you are not! 
absolutely delighted with the results. 
Make no mistake, this is a real radio, not a ' 
toy or crystal set! Fully built and tested, 
ready for immediate use. NO EXTRAS, 
This minute radio will play anywhere — any* 
time, beach, garden, park, home, office, 
school, etc. The super sensitive 6 transistor 
circuit is fully tuneable over both long and 
medium wavebands, with built-in ferrite 
rod aerial to provide excellent selection. 
The Orion operate* from one tiny battery, either mercury or nickel cadmium, 
for tone life and economical running cost. The output is vfa a crystaUeype 
personal earphone, giving extreme clarity, which prevents disturbing other 
people when used in public parks, open spaces, etc. The small size of the 
Orion allows it to be carried easily in the pocket or handbag, and it is also 
supplied with an attractive presentation case. Complete with earpiece, 
battery and carrying case. 

Specification: Waveband coverage. Medium SISkc/s to l,605kc/* a Long 
iSOkc/s co 3Q8kc/s. Sensitivity: 55mV/m max. Selectivity (at -30kc/s detun- 
ing)— lOdB. Power consumption: 4mA max. Power source: 1 x 1.4V Mercury 
battery. Mallory type RM625 or equivalent. Malfcry battery is not recharge- 
able. 




COMPLETE WITH EARPIECE 
RECHARGEABLE BATTERY 
POCKET CARRYING CASE 



ONLY posT 

£1.48 '*■> 



'S pare rechargeable battery tap antra — post FREE with radio. 

BARGAIN PACKAGE 

COMPRISING— I ORION RADIO 
I RECHARGEABLE BATTERY AND 
BATTERY CHARGER 



£2 



POST 
20p 



BATTERY CHARGER 

THE BATTERY WE SUPPLY WITH THE ORION IS A RECHARGEABLE 
TYPE. BATTERY CHARGERS ARE AVAILABLE TO RECHARGE THE BAT- 
TERY AGAIN AND AGAIN. OPERATES ON HOME MAINS 200/240 VOLTS 
A.C. 

Bauer/ life is approx, 10 hours. Charging time: 10 hours. A ipare battery 
will enable you to keep your Orion constantly in use. 

LAS! IICE 8Sp. post free with radio 



EXCLUSIVE 

MODEL TM-l 1000 ohms; v 

MINI-TESTER 

The first of Lasky's new-look top value meters, 
the TM-l is a really tiny pocket multimeter 
providing ' 'big'* meter accuracy and perfor- 
mance. Precision movement calibrated to -fc 3 i% 
of full scale. CSick stop range selection switch. 
Beautifully designed and made impact resistant 
black case — with white and metallic red/green 
figuring. Ohms zero. 

• DC^V; 0-10-50-250-1,000 at IK/OPV, 

• AC/V: O-IO-50-25O-I.0O0 at IK/OPV. 

• DC CURRENT: 0-1 mA, lOOmA. 

• Resistance: 0-ISOkO. 

• Decibels: — lOdB to 4- 22dB. 

• Complete with test leads, battery and 
instructions. 

LASKY'S PRICE £1 .95 POS T I3 P 

MODEL TM-5 5k OHMS/Y POCKET MULTIMETER 

Another new look pocket multimeter from 
Lasky's providing top quality and value. The 
. shmline" impact resistant case — size: 4£in. X 
2iin X l|in. fitted with extra large 2 Jin square 
meter. Readability Is superior on all low ranges; 
making this an excellent instrument for ser- 
vicing transistorised equipment. Recessed click 
stop selection switch. Ohms zero adjustment, 
Buff finish with crystal clear meter cover 

• DC/V: 3-1 5-1 50-300- 1. 200 at 5K/OPV. 

• AC/V: 6-30-300-oOO at 2-5K/OPV. 

• DC Current: O-330/jA, 0^300mA. 

• Resistance; 0-1 OkQ, 0-1 MfJ. 

• Decibels: — lOdB to +l6a'B. 

• Complete with test leads, battery and 
instructions. 

LASKY'S PRICE £2.9S post ij p 



TMI & 
TM5 





■ in I? A Mcdonald 

lYlr .DU SERIES FOUR ! 



PROFESSIONAL 
SINGLE 



PLAY UNIT 



High-precision 
low- mass fully 
counterbalanced 
pick* up arm, heavy 
balanced turntable, 
simply operated 
controls, viscous 
cueing device, 
slide-in cartridge 
carrier, four pole 
motor. 



LASKY'S PRICE 

£12.50 




post 35p 



Post 40p 



SS&BS. LASKY'S PRICE £15-75 
610 AUTOMATIC TURNTABLE 

Same specifications as the MP60 but with synchronous four pole motor and 
full automatic change facilities. 

LASKY'S PRICE £1!>.45 Post 35p 

WITH PLINTH AND COVER £18.75 POST 40p 

510 AUTOMATIC TURNTABLE 

Counterbalanced pick-up irm, pressed steel turntable, bias compensator, 
viscous curing and synchro ioui four pole motor. 

LASKY'S PRICE £13.49 POST 35o 

WITH PLINTH AND COVER £16.95 POST 40p 

310 AUTOMATIC TURNTABLE 

Low-mass square section pick-up arm, cue and pause lever, visual atylus 
pressure indicator, slide-in cartridge carrier, four pole motor. 

LASKY'S PRICE £9,95 POST 35p 

WITH PLINTH AND COVER £13.45 POST 40p 



bsr Mcdonald packages 

PACKAGE No. 1 

BSR McDONALD 5I(i 4 Speed Autochange £17.00 

AUDIO DEVELOPMENT AD76K. Magnetic Cartridge £ 4.50 

BSR Afromosia Plinth with black mounting board £ 5.00 

BSR Smoked Perspex Dust Cover £ 3.50 

Recommended retail price ....£30,00 

LASKY'S PRICE £25.25 post « p 

ADD £5.50 if Mil (Ml/ E it preferred 
ADD £6.50 if Shure M44/5 ii preferred 



PACKAGE No.2 

BSR McDONALD 3Ki4 Speed Autochanger £14.00 

AD76K Magnetic Cartridge £ 4.50 

BSR A from os ia Plinth with black mounting board £ 5.00 

BSR Smoked Perspex Dust Cover £ 3,50 

Recommended retail price £27.00 

LASKY'S PRICE £23.50 

ADD SQp if BSR Ceramic Cartridge is preferred 



NOW AVAILABLE laskys exclusive 

£4.75 POST 2Sp 



LASKY-McDONALD 
plinth and cover 
available separately at 



WAFER TYPE ELECTRO DYNAMIC 



This revolutionary idea i i sound reproduction functions 
in a similar manner to the cone loudspeaker system. In 
place of the conventional aaper cone is a flat, rigid plastic 
panel only a fraction of the depth of the equivalent cone 
structure. Witn a flat rectangular panel a larger piston area 
is also available thereby reducing the size compared with 
an equivalent cone loudsp jaker. 

Power capacity: 20 watts peak). Freq. range, 40H1-20.000 
Hi. Input imp,: 6 ohms, Siie: Miin X 14+iin x 1-rVin. 

LASKY'S PRICE £5.75 each £1 " 




Only 

1-rV* THICK 11 

for two. Post 20 p each 



994 



I 



DM 



HIGH PERFORMANCE 11 TRANSISTOR THREE 
WAVEBAND PORTABLE BATTERY/MAINS RADIO 

I This is a realty top performance, top quality solid state receiver packed with SONY know-how and backed by tne 
I outstanding reliability for which SONY are renowned. Nov/ this outstanding see is available from Lasky's at over 
|27% below the manufacturer's list price making it without a doubt the NUMBER ONE SCOOP of I97U Just loot 
lit these outstanding features. Covers MW, LW and FM (VHP). 1 1 transistor circuit for high sensitivity and stability 
I Powerful output to S" P.M. Dynamic speaker with rich clear tone quality. AFC for drift free VHP reception. Push- 
I button wavcchange selectors and tone control. 

I Choice of three power sources— 9V battery, household mains or car battery with suitable adaptors. Dial light for 
I use in the dark. External tacks for earphone, tape recording, external power input and car aerial. Ultra modern 
I styling and superb finish with padded leatherette covered cabinet for superior sound damping with chrome trim, 
[strong carrying handle. 

I The SONY TFM 8030L will enliven your leisure hours anywhere, anytime with exciting sound, news, sport, music, 
letc. Technical specification: Freq. range, FM 07-IOSMHz, LVVI50-Z85kHj!, MW530-I ,605kHz. Circuit: II transistors, 
|7 diodes and 2 thermistors. Aerial System: Directional telescopic for FM, internal ferrite bar for LW/MW. Power 
■ Output: I.85W max. Speaker PM Dynamic — 4Qimp. Power Source: 9v power pack battery (Ever-Ready PP9 or cquiv.}. 
I AC mains with adaptor. Car battery with adaptor. Size: ?S(W) x B A(H) x 3S(D)- Complete with earphone and battery 
land full instruction manual. 



MANUFACTURER'S LIST PRICE £29.75 

LASKY'S SPECIAL 
OFFER PRICE 



£21.50 



Optional Extras. SONY 
AC-90O AC adaptor £4.00 DCC 
car battery cord £6.00. Both post 
purchased with radio. 

Post J5p 




DIGITAL CLOCK 





SCOOP! 



• HADE ESPECIALLY FOR 
LASKY'S BY FAMOUS 
MAKER 

• MAINS OPERATION 

• 12 HOUR ALARM 

• AUTO "SLEEP" SWITCH 

• HOURS, MINUTES AND 
SECONDS READ-OFF 

• FORWARD AND BACK - 
WARD TIME 
ADJUSTMENT 

• SILENT OPERATION 
SYNCHRONOUS MOTOR 



• SHOCK AND VIBRATION 
PROOF 

SPECIAL QUOTATIONS • BUILT IN ALARM 

FOR QUANTITIES BUZZER 

This unique DIGITAL CLOCK la now available EXCLUSIVELY FROM 

LASKY'S In chassis form for you to mount In any housing that you choose. 

All settings are achieved by two dual-concentric controls at the front including: 

ON-OFF-AUTO and AUTO ALARM, "sleep" switch, 10 minute division "click" 

set alarm (up to l2-hou« delay), time adjustment. Ultra simple mechanism and 

high quality manufacture guarantee reliable operation and long life. 

The sleep switch will automatically turn off any appliance— radio, TV, light etc. 

at any pre-set time up to 60 tnln. and In conjunction with the AUTO setting will 

switch on the appliance again next morning. 

The clock measures 4iW x 1JH x3iD (overall from front of drum to back of switch) 

SPEC: 210,240V AC, 50H* operation; switch rating 250V. 3 A. Complete with 

Instructions. HUNDREDS OF APPLICATIONS. COMPLETE WITH KNOBS 

LASKY'S PRICE £6.95 p*tt* 

SPECIAL QUOTATIONS FOR QUANTITIES 



mm * n \ 



A completely new design 20,000 O.P V. pocket 
multimeter with mirror scale and built-in thermal 
protection. Exceptionally large easy to read meter 
with D'Arsonval movement. Colour coded 
scales. Single positive click-In, recessed selec- 
tion switch lor all ranges. Ohms zero adjustment. 
Range spec. a.c. volts: 0-6-30-300- 1.200V at 
10Kfohms,V. OC volts: 0-3-15-1 5O-3O0-t.2KV at 
MKfohms/V. Resistance: 0-60K-6megs. DC 
current: 0-80|jA — 300 mA. Decibels: -20dB to 
-I- 17 dB. Extremely high standard of accuracy 
on all ranges. Uses onellVp en light battery. Strong impact resistant plastic cabinet 
— size only 41 x3jx 1^-in. Two colour buff/green finish. Complete with test leads and 




battery. 

LASKY'S PRICE 



£4.25 




Projected Is a range of modules which connect together to form a complete 

•tsrso amplifier. The modules are : 1. Z-J0 high gain power amp. 2. Stereo-M 

pre-amp. control unit. 3. The PZ-S unitabillsed and PZ-S stabilised power 

supplies. A complete system comprises two Z-M's T on* Stereo-M and a 

PZ-S or PZ-t. 

STEREO SO SPECIFICATION ' ' .. 

rnput sensitivities: Radio up to 3mV, Magnetic Pick-up 3mV: correct to R.I, A. A. 

curve ±1dB| 20 to 25,000Hz. Ceramic PI ctt-up to 3mV: 

Auxiliary up to 3mV • Output: 1 volt • Signal to 

noise better than TOdB • Front panel: brushed xf&.9a Post I So 

aluminium with black knobs and controls* Slie: ssssswwsp 

5*xHx41n. 

Z-30 SPECIFICATION 

• Power output: 15 w. R.M.S. Into 5 ohms using a 35 volt supply • Frequency 

response: 30 to 300,000Hz ± 1dB • Distortion: 0.02% s) Signal to noise: better 

than 70dB • Input sensitivity: 250mV Into 100 K ohms • Loudspeaker Imp: 

3 to 15 ohms • Power requirements: from 8 to 35V 

DC (The Z30 will operate from batteries If required)- £A.2S Post 18p 

Size; 3±x2i-x+in. -- 

30V unstablllaed— sufficient to drive two 

Z-30' a and a Stereo 60 for domestic £4. SO Post ,3 p 

applications. 

35V stabilised — ideal for driving two 

Z-30's and a Stereo SO for low efficiency 

speakers. 



PZS 
PZ6 



Z-30 ' s and one PZ-5 



£7.50 
£19.25 



Post 13p 



OUT NOW 



LASKY'S NEW 1971 

AUDIO-TRONICS 

CATALOGUE 



Send your name and address and I3p for post and 
inclusion on our regular mailing list. 



707 EDGWARE ROAD. LONDON. W.2. 



Tel: 01 -723 3271 



33 TOTTENHAM ,CT.RD, LONDON, WtP 9RB. Tel: 01-636 2605 



Tel: 01 -353 5812 



162/3 FLEET STREET. LONDON, EX.4. 



Tel: 01 353 2833 f- 



HIGH FIDELITY A UDIO CENTRE \ 

42-45 TOTTENHAM CT. R0, LONDON. W1P 3RD. Tel: 01-580 2573 



I 42 -45 TOTTENHAM CT. HD, LONUUN. wir a«u. lei: ui-shu io/J XSC t m. - 
Opon all day. 9 - m -6 p.m Monday lo Saturdav ^"C^lti^ 

ALL MAIL ORDERS AND CORRESPONDENCE TO: 3-15 CAVELL STREET, TOWER HAMLETS, LONDON, El 2BN Tel: 01-790 4821 



995 



BENTLEY ACOUSTIC 
CORPORATION LTD. 

38 CHALCOT ROAD, CHALK FARM, LONDON, N.W.I 
THE VALVE SPECIALISTS T«t«phem« 01-722 9090 



0A2 
OB 1 

1A7GT 

IH5GT 

LL4 

1HGGT 

IKS 

IB* 

iss 

1U4 

1U5 

2D21 

3Dfi 

3Q4 

3QSGT 

3S* 

3V4 

SV4G 

6YSUT 

5Z4Q 

6/30L2 

SASG 

8AC7 

SAGS 

5AK5 

8AL5 

6AQ0 

SATS 

8AU0 

6AV6 

SB6G 

flBAB 

8BEH 

SB US 

SBJS 

BBQ7A 

BP.K7 

6BR8 

6BW8 

8BW7 

SBZS 

SC9 

6CD6G 1 

80HS 

6CL6 

ecw* 

6F1 
8F6 
8FSO 



8F13 

CF18 

6F23 

6P24 

*JF23 

SF28 

6H6GT 

SJ5G 

6J8 

0J7G 

637GT 

6K7G 

6K7HT 

8K8G 

6L6GT 

6L7GT 

8L18 

6LD20 

62S7GT 

6Q7 

SQ7G 

8K7 

6B7G 

6SA7GT 

SSA7M 

SSCiiJT 

6SG7GT 

88H7 

68J7 

6BK7QT 

6SQ7<;t 

6VBG 

SV6GT 

SX4 

6X5 GT 

7Bfl 

7B7 

70S 

7H7 

7B7 

9D7 

10C1 1 

iocs 

1GFI 

10F9 

10PJ8 

1QI.D11 

10F13 

10P14 1 



.88 10P18 



la AS 
1SA06 
12AD6 
l:AEG 
12ATS 
12AT7 
H1AU6 
12AU7 
12AVS 
12AX7 
12BA6 
12BF.B 
12BH7 
12E1 
12J7GT 
45 12K6 
12K7GT 
12Q7GT .28 
12SA7GT 

.40 
128CJ .35 
128G7 ,B3 
12SH7 .16 
12SJ7 .88 
123K7 .84 
128Q7GT 

.GO 
1487 1.16 
19AQ5 
20 F*J 
20L1 
20P1 
20 P3 
20P4 
20PS 
25A6G 
25L6G 
25 TS 
25 YOG 
25Z4G 
25Z6 
±r>7AG 
30CJ 
30C15 
30C17 
30C1S 
S0F5 
30FL1 



,75 



30FL2 
S0FL12 .80 
30FL14 .73 
301,1 
30 LIS 
301,17 .78 
30P4MB .88 
30F12 .68 
S0F19/ 

S0F4 .80 
S0PL1 .68 
30PL12 .87 
S0PL13 .78 
S0PL14 .75 
30PL1S .88 
3SL6GT .44 
35W4 .83 
35Z4GT .84 
3555BOT .30 
50MGT -46 



.26 



72 



,3'i 



85A2 .43 
807 .59 

6763 .80 

ACS/ PES 

.98 
AC3/PES/ 

Hi i .98 
ACflPEN.38 
AC/PES(7) 
.88 
AC/TH1 .50 
AC/TP .98 
AX80 .78 



ATP4 

A 31 

AZ31 

AZ41 

B3B 

CY1C 

CY31 

DAC32 

DAFS1 

DAF98 

DF83 

DF01 

DF9S 

DP97 

DB63 



1.HJ.78 .88 
DK77 .80 
OK40 .68 
DKS2 .43 
DK98 .87 
DL98 .87 
DM70 .80 
DM71 .88 
DW4/ 

350 .88 
DW4| 

COO .88 
DY86/7 .88 
DY802 .48 
E80F 1 . 20 
E8SF 1 
BS8CC .60 
E180F .86 
E1H2CC1.13 
K1148 .53 
EA50 .18 
EA76 .88 
EABCBO .33 
EAC91 .88 
EAF42 
EB34 
KIWI 
EB91 
EBC41 
EBC31 
EBG91 
EBF80 
HBP88 
I 1F8S 
EBL21 
EC86 
USB 
EC22 
ECG33 1.68 
EQC40 

i:ccs I 

ECCSS 
EOC83 
F.CC84 

lines;. 

ECC86 
BCC88 
ECC1B9 ,48 
EOC804 .58 



. Sd 



ECC8071.85 
BCF80 .38 
EOF82 .88 
ECF88 .65 
ECF8048.10 
ECH21 .63 
ECH35 .89 
ECU 42 
ECHS1 
ECH83 
ECH84 .38 
ECE80 .36 
ECL82 
ECL63 

EOL85 
BCLBS .40 
EF23 .88 
EF3B 
EF37A 
EP3B 



EF41 

EF42 

EF64 

EF73 

EF80 

EF83 

EF85 

EF86 

EF89 

EF91 

EF92 

EF97 

H8M 

KF183 

EF184 

EH90 

ELS2 

EL34 

EL 37 

EL41 

EL42 

EL81 

EL83 

EL84 

EL85 

ELBA 

EL91 



EL95 

EM34 

EM80 

EM81 

EM84 

EM87 

EY51 

EY81 

EY83 

EY84 

EY86/7 

EY88 

EY91 

EZ40 

EZ41 

EZSO 

EZ81 

EZSO 



.35 

.90 
.3S 
.42 
.84 

,3S 

.37 
.85 
.55 

.50 
.33 
,43 
.53 

M 

.43 
.23 
,M 
.83 
FW4/000.75 
FW4/800.75 
GZ30 .35 
GZ32 .45 
GZ33 .70 
GZ34 .58 
GZ37 .75 
KABC80.45 
HL23DD.40 
FTL41DD.98 
HL42DD.50 
1IS309 1.38 
HYR2 .53 
HVH2A .58 
KT2 .85 
KT8 1.73 
KT44 1.00 
KTSB .83 
KT88 1.70 
KTW61 .83 
KTW62 .83 
KTWSJ .60 
MHLD6 .75 



OTS 2.05 


PL S3 .88 


0?41 


M 


AC107 


.15 


BGZ11 .38 


S308 .98 


PLS4 .38 


CTP42 


.80 


AC113 


JN 


BD119 .45 


S339 1.86 


PLS02 .80 


trpao 


.35 


AC 127 


.20 


BF159 .85 


P81 .80 


PL500 .68 


i; [■'85 


.31 


A0128 


.20 


BF1B3 .80 


PABCBO .86 


Pl.fn.i .88 


XJFS6 


.33 


AC15S 


.20 


BF173 .33 


PC86 .68 


FL506 1.44 


UF89 


,M 


AC157 


M 


BF180 .80 


FC88 .58 


PLfiOS 1.40 


UL41 


,11 


AC16S 


,tt 


BF181 .40 


F095 .53 


r-js;,w 1.44 


UL84 


.ita 


AC168 


,M 


BF185 .40 


PC97 .40 


PL802 .76 


CM80 


.33 


AC176 


.66 


BFY50 .23 


PC9O0 .38 1 PM84 .39 


EY1N 


.50 


AC177 


■ S3 


BFY51 .19 


PCC84 .8B1PX4 1.18 


CY21 


.55 


ACY17 


.M 


BFY62 .20 


PCC85 .88 PX36 1.18 


CY41 


.88 


ACY18 


,n 


BY100 .18 


POC88 .49 PY32/3 .60 


tY85 


£9 AOY19 


,10 


BYlOfl .18 


PLX.-89 .48 PY80 .88 


tio 


.45 


AOYaa 


,18 


BY114 .13 


PCXJ189 .49 PY81 .27 


112/14 


M 


ACY21 


.19 


BY126 .15 


PCC805 ,84 PY82 ,87 


118/20 


.75 


ACY22 


.15 


BY137 .18 


PCF80 .80 PY88 .89 


ris 


.73 


ACY28 


.18 


BYY231.0O 


PCFS2 .83 PV88 .34 


1 T 22 


,3S 


AD 140 


.38 


BYZ10 .86 


PCF84 .40 PY600 1.08 


IF25 


M 


AD149 


.yj 


BYZ11 .86 


PCF86 .50|PY800 .88 


IF26 


,5» 


AD 161 


.45 


BYZ12 ,26 


PCF200 .87 


PY801 .84 


U45 


.73 


AD163 


.45 


BYZ13 .26 


PCF801 .36 


PZ30 .48 


U191 


fta 


ADT14C 


,«a 


GG12E .20 


PCF802 .46 


QQVOS/10 


D^Sl 


.73 


AF102 


.90 


F9Y11A .88 


PCF805 ,84 


1.20 


11281 


,40 


AF106 


,50 


GD9 .80 


PCF806 .84 


QV04/7 .83 


1T282 


,48 


a: 'ii4 


.25 


GET113 .80 


PCFS08 .78 


BIO .78 


17301 


.53 


AF115 


.15 


GET116 .40 


PCB200 .88 


Ell .98 


17403 


.33 


AF1I7 


. M 


GET118 .20 


PCL82 .87 


BIS 1,76 


U404 


.38 


AF121 


..30 


GET119 .80 


PCL83 .50 


E17 .88 


1JB01 


.to 


A F124 


.88 


GET573 .38 


POL84 .38 


B19 .33 


•J4020 


,33 


AF128 


,U 


GET587 .43 


FCL805/S5 


8P42 .76 


YP23 


.40 


AFI39 


,B5 


GBT873 .15 


.45 


SP61 .33 


VP41 


Jfi 


AP178 


M 


GET8S7 .88 


I'CLSvl .43 


TII4B .60 


.'BIOS 


.33 


AF180 


M 


GET897 .88 


PCL89 .76 


TII233 .88 


i'BlSO 


.33 


AF186 


M 


GET898 .83 


FD50O 1.44 


TP2820 .98 


.TBI A 


,i [ » 


AP239 


.38 


HI .16 


PBN4DD 


UABC80 .33 


if 0111 


.44 


B1181 


50 


H3 .15 


1.38 


UAF42 .58 


ruiao 


M 


BA102 


.15 


MAT! 00 .39 


PEN38C .75 


DBC41 .46 


VTJ120A 


.tiU 


BA115 


.14 


MAT101 .43 


PES45 .35 


URL'S 1 .40 


1TH33 


.35 


BA116 


.M 


MAT120 .38 


PES4SDD j UBF80 .89 


SF7B 


84 


BA129 


.U 


MAT121 .43 


.76 CTBF89 .84 


W107 


M 


BAI30 


10 


OA5 .88 


PBN46 .80 C3L21 .65 


W729 


M 


BC107 


.13 


OA9 .13 


, PEN T 453DD ]UC92 .85 


X41 


,M 


BC108 


.13 


GA10 .48 


.88 


UOC84 .40 


£61 


M 


BC1I3 


,?5 


OA47 .10 


PESDD- 


t*CC85 .37 £65 


.50 


BC115 


.15 


OA70 ,L5 


4020 .88 


UCFBO .42 


K68 


M 


BC116 


.25 


OA73 .18 


PFL200 .69 


UGH21 ,80 


JS323 


M 


BC118 


M 


OA79 .09 


PL3S .48 


TJGH42 .63 


4A119 


.18 


BCY10 


M 


OA81 .09 


PLS1 .48 


UCH81 .33 


4A120 


.15 


BCY12 


M 


OASG .08 


PL81A ,63 


UCLS3 .86 


AA129 


.15 


BCY33 


M 


OA90 ,13 


PL82 .83 


UCL83 .50 


LAZ13 


.18 


BCY38 


,23 


OA91 .09 



OA95 


.09 


OA200 


.03 


OA202 


.10 


OC22 


38 


OC23 


,38 


OC24 


,3S 


ocas 


.38 


OC28 


,25 


OC3S 


.60 


OC29 


,S3 


OCS6 


.32 


OC36 


.43 


0C42 


.63 


OC43 


1.1S 


OC44 


.10 


OC45 


.13 


OC46 


.15 


OC70 


,1S 


OC71 


.13 


0C72 


.13 


OC74 


.23 


OC76 


.13 


OC76 


.15 


OC77 


.27 


OC78 


.15 


OC78D 


.15 


OC81 


.13 


0O81D 


.13 


oca 2 


.13 


OC82D 


.15 


OC83 


.20 


OC84 


.24 


OC123 


.23 


OC139 


.£3 


OC140 


.95 


OC1S9 


.23 


OC172 


.35 


OC200 


.22 


OCS01 


.38 


OC202 


.43 


OCS03 


.30 


OC204 


.30 


OC20S 


.43 


ORP13 


.53 



AB valves are annsed, boied, and subject to the standard 90 day guarantee. Terms of business 
Cash or cheque with order only. Post/pactcing 3p per item, subject to a minimum oi 9p, Orders over 
75.00 post/packing free. Same day despatch by first class mail. Any parcel insured against damage 
in transit for only 3p eitra per order. Complete catalogue with conditions ol sale price 7p post paid. 
Business hours Mon.-FrL 9^5.30 p.m. 3»ts. 9-1 p.m. 

We do not handle second* nor rejects, whith are often deswlbed as "Sew and Tested" bat have a 
limited and unreliable life. So enquiries answered unless 8.A.B. Is enclosed lor reply. 



The Unique 

MULTI-MINI TWIN-VICE 




An extra "Pair of hands*' for 

those tricky jobs 

ASSEMBLY— SOLDERING— 

GLUING— WIRING— DRILLING 

ETC. 

• INDEPENDENT ADJUSTMENT OF 
THE TWO VICE HEADS TO ANY 
ANGLE WITH POSITIVE LOCKING. 

#JAWS WILL FIRMLY GRIP, ROUND. 
FLAT, SQUARE, OR HEXAGONAL 
PARTS. 

TWIN VICE; £5.90 (24? P & P) 

ALSO AVAILABLE 

SINGLE VICE; £3.374 (20p P & P) 

COVENTRY MOVEMENT CO LTD. 
BURNSALL ROAD, COVENTRY 

CV5 6BU STD 0203-7H363 



996 




£6.75 



SjfF' Solve your communica- 
tion problems with this 
4-StatlOD Transistor Intercom syntm !l master and 
8 SuiiJ, in de-luie plastic cabinets for desk or wall 
mounting. Call/talk/listcn from Master to Subi and 
Saba to Master. Ideally suitable for Business, Sur- 
gery, Schools, Hospital, Office and Home. Operates 
oa one 9V battery. On/off switch. Volume control. 
Complete witn 3 connecting wires eaca 66ft. and 
other accessories. F. & F. £0.40. 

MAINS INTERCOM 

Ho batteries — no wires. Just plug in the mains 
lor instant two-way, loud and clear communication. 
On oil switch and volume control. Price £18. 96. 
P. * P. £0.45. 




OUR 
'RICE 
ONLY 

£3.15 

Same as 4-Sfcanon^niWrcom for two-way instant 
communication. Ideal as Baby Alarm and Door 
Phone, Complete with 66ft. connecting wire. 
Battery £0.12. P. & P. £0.25. 




£2.98 

iy not boosi; 
business effi- 
ciency with this incredible De-luxe Telephone Ampll* 
fler. Take down long telephone messages or converse 
without holding tne handset. A useful office aid. Oof 
OS switch. Volume Control. Battery £0.12 extra. 
P. & P. id .18. Full price refunded if not satisfied In 
7 days. 

WEST LOSDOH DIRECT SUPPLIES (PW.X) 
169 EESSIHQTOJt HIGH STBEET, LONDON, W.8. 



NEW RANGE IMF. TV AERIALS 

All U.H.F. aerials now fitted with tilting 
bracket and 4 element grid reflectors. 
Loft MonntinE Arrays. 7 element £2-25. 
11 element £2 62*. 14 element £3 00. 
18 element £3 SO. Wall mounting with 
Crunked Arm. 7 element £3 ■ 25. 11 element 
£3-75, 14 element £4- 121. 18 element £4-50. 
Chimney Mounted Arrays complete. 7 ele- 
ment £4-00. II element £4-371. 14 element 
£4 '75. IS clement £5-25. Complete assembly 
instructions with every aerial. Low Loss 
co-axiaf cable 81k yd. King Teleboosters — 
Lab gear U.H.F, Boosters from £3-75. 
Belling Lee 'Concord' all band V.H.F./ 
U.H.F. mains operated pre-amp £7 50. 
Slate clearly channel number required on all 
orders, p.p. Aerials 40p. Accessories 15 p. 
C.W.O. or C.O.D. 

BBC - ITV- FM AERIALS 

B.B.C. (Band 1) Loft £1 - 25. 
Wall S/D £1-621, 'H' array 
£3-00. ITV (Band 3) 5 ele- 
ment loft array £2-25. 
7 element £2-75. Wall 
mounting 5 element £3-25. 
Combined BBC/ ITV loft 
I + 5 £2-75. 1 + 7 £3-371. 
Wall mounting 1 +5 £3- 871. 
Chimney mounted 1 + 5 
£4 • 50. Preamps from £3-75. 
Combined BBC/ITV/BBC 2 
aerials 1 + 5 + 9 £4 00. 
1 + 5 + 14 £4-50. 1 = 7 = 
14 £5 00. Available loft only. FM radio 
loft 8/B 97 ip. 'H' £1-921. 3 element array 
£2 '871. Standard co-axial cable 5r> yd. 
Coax plugs 8 ip. Outlet boxes 30p, Diplexer 
crossover boxes 87 4p p. & p. Aerials 40p; 
accessories ISp C.W.O, or C.O.D. (Min 
C.O.D. charge I71p.> 5p for fully illustrated 
lists. 

Callers welcomed — open all day Saturday. 

K.V.A. ELECTRONICS (Dept. P.W.) 

40-41 MONARCH PARADE, 

LONDON ROAD, MITCHAM. 

SURREY 01-646 4834 



I 




PHILIPS STEREO 
AUTOCHANGER 
£8.75 X 

Precision hi-fi quaillr 

at bargain price. 

Silver and zrey 

deck enamelled linisb, 10' in. dia. turnislile. 4 speeds, 

IS, S3* 45, and 78 rpm. Plays 7, 10, 12in. discs wnicb 

can be mixed. Fitted renowned Philips plug-in Xtal 

AG33D6 with dual sapphire stylos for LP 'E P.. 78. 

Sensitivity 100m V. Frequency response 30cpt-lBKc/a. 

Lightweight stylus pressure 3-6 grammes. Board space 

required 1* X 181 in. Above tin. Below 2 J in. 12 montb 

guarantee. (Alio available with GP31Q diamond stylus LP 

Stereo/EP and Sapphire 78. £1 eitra). 

HATCHED TEAK PLINTH with PLASTIC COVER. 

Only 16 extra or Cut -out plywood base board 50p extra. 



BSR 



4-SPEED SUPERSLIM 
AUTO RECORD CHANGER 



Plays 12". 10" or 7" records. 
Auto or Manual. A high 
quality unit backed by BSR 
reliability with 12 months' 
guarantee. Size 13* 
11] in. Above 
motor board 3] in. 
below 2 r in. AC 2OO:250v. 

with STEREO/MONO XTAL £7 Post 2Sp 

BSR Minichsnger OA50 Stereo Mono. 

Plays 13", 10' or 7" records. 

Blaa 12 x 8) la. AC 200 250?. 




(Q Post 
t0 25p 



GARRARD PLAYERS with Souotone 8TA Cartridges. 
Stereo Diamond Mono Sapphire, SP2S Mlt II £15 
Model 3000 Stereo/Mono Auioehanger £13. Post 25p. 
Model 3600 Stereo/Mono Autochauger £14. Post 25p. 
RECORD PLAYER PORTABLE CABINET £\ TC 

Space lor amplifier and autoehauger. Post 26p. "■■*• ' -' 
RCS DE-LUEE 8 WATT AMPLIFIER. Ready made 
with 2-stage trtode pentode valve, 3 watts output. Tone 
and volume controls. Isolated mains transformer, knobs, 
loudspeaker valves ECLS2. EZS0. I A 

Response 50-12.000 cps. Sensitivity 200toV. Post £5p, 
RSC 2 WATT AMPLIFIER with loudspeaker £J 



and valves TJCLS2 and UY85 



Post 25p 



R.O.S. TEAK WOOD BABE. Ready cnl nut £7 25 

iormoantlng (State player make and model) •»•*•*•# 

R.C.S. PLASTIC COVERS FOE ABOVE BASE. £\ 25 

Durable tinted plastic, attractive appearance. *—**^*. 



EMI PICK-UP ARM with mono xtal and stylus £1-25 
EMI JUNIOR 4 SPEED RECORD PLAYER £\ Post 
Mains operated motor, turntable and pick up *"* 25 p. 
HI-FI PICK-UP CARTRIDGES. Diamond Stereo.Mono. 
OTA £2-90; GF84 £2 75: GPflS £2 25; Mono GF&l £1 80; 
GC8 £1-25; GP87 95p. ACQS L.P. only 50p. 
All standard fixing complete with stylus. 



WEYRAD P50— TRANSISTOR. COILS 



RA2WFerrite Aerial, . S5p 

Osc. F50/1AC SQp 

I.F. F50/2CC 470 kc/s. 83p 

8rd I.F. P50/3CC 8S» 

P51/1 or F51/2 8So 

P50/3V 33p 



Spare Cores 3p 

Driver Trans, LFDT4 , 50p 

Printed Circuit, PCA1 . 5 Op 

I.B. Tuning Gang B5p 

Weyrad Booklet lOp 

opn ssp 



Mnllsrd Ferrite Rod 8 x iin. EOp, 6 x jin. 25p. 



VOLUME CONTROLS 

Long spindles. Midget Size 
5 K. ohms to 2 Meg. LOG or 
LIN. L/S lop, D.F. 26p. 
STEREO JJS 55p. D.P. 75p 



SOohm Coax 4p. yd. 

BRITISH AEEIALITE 
AERAXIAL-AIR SPACED 
40 yd, £1 40; 60 yd. £2. 



FRINGE LOW LOSS I fj n - 
Edge 6K, S.P. Transistor 25p I Ideal 825 and colour. ■ **r 10 - 



WIRE- WO HMD 3- WATT POTS. 
Small type with email knob. 
Values 10 Q to 30 K., 
Carbon 30 K to 2 meg. 



25p 



WIRE-W0DND3-WATT 
STANDARD SIZE POTS. 
LONG SPIKDLE A(\ n 
10 OEMS to 100 K ~ W P 



VEROBOARD 16 MATRIX 
2j x 5in.19p.2i x 3Jun.lSp.3J x 3Jin.19p.8I x Sin. 2fip. 

EDGE CONNECTORS 16 way 25p; 24 way 38p. 

PINS 36 per packet 17p. PACE CUTTERS 3Sp. 
8.R.B.F. Board 015 MATRIX 2Hn. wide 3p pec lin., 
3»in. wide 4p par 1 In. : Gin. side 5p per 11a. (tip to 17hU. 
B.R.B.P, undrilled ,V in, Board 10 x Sin, lBp. 



BLANK 


ALUMINIUM 


CHASSIS. 


IS 


I.W 


g. 


2 iin. aides. 


8 x 4in. 


45p; 8 x Bin. 


G0p: 10 x 


Tin. 


N»j 


14 


X Sin. SOp; 


IS x Sin 


. 90p : 12 x Sin. 90p, 










ALUMINIUM PANELS 13 s.w.g. 6 


X 4in. 8p 


1 I 


X Sin. 15p; 


10 x 7in 


17p; 12 x 81 


X 23p;14 x 


Sin 


.-■■',■ 


la 


X 12iu.32p. 



11 inch DIAMETER WAVE-CHANGE SWITCHES. 

2 p. 2- way, or 2 p. 8-way or 3 p. 4-way 2Gp each. 1 p. 13-way, 
or 4 p. 2-wf.y. or 4 p. It-way 25p each. 1 Inch DIAMETER 
Wavechange "MAKITS" 1 p. 12-way. 2 p. 8-way, 3 p. 
4-way, 4 p. 3- way, B p. 2- way, 1 water BOp, 2 water SOp. 

3 waler £1.20, 4 water £1.50, 5 waler £1.80, 6 water £2,10 
TOGGLE SWITCHES, sp. 14p; dp. 18p; dp. dt. 23p. 



ALL PURPOSE HEADPHONES 

H.R. HEADPHONES 200 ohms Super Sensitive . . 21-75 
LOW RESISTANCE HEADPHONES 3-5 ohms . . £2 00 
DE LTJKE STEREO HEADPHONES 8 ohms . £3 25 



GENERAL PURPOSE TRANSISTOR 
PRE AMPLIFIER BRITISH MADE 

for Mike, Tape, F.U., Guitar 
Battery B-12v or H.T. line 200-30Qv D.C. operation. 
Size 1]* >l; - i }'. Response 25 c.p.s, to 25 Ks/s. gSdb gain. 
For use with valve or transistor equipment. 
Full instructions supplied. 00 n Fo,t 



Brand new. Guaranteed. Details S.A.E. 



lop 



NEW TUBULAR ELECTROLYTICS 



2,'350V . . 


14p 


4/350V . . 


14p 


8 '450V . 


lip 


16/460V 


lap " 


88/450V 


20p i 


25/25V 


10p 


50/50V . . 


lOp 1 



CAN TYPES 
18+18/5007 .. 
50-f 5G/850V . . 
SO + 100/350V.. 
32 + 32/250V .. 
32 + S2/450V .. 
32-32 + 32,'S50v* 43p 
100-r50-60/350V48p 



55p 
35p 
68p 
18p 
33p 



10O/25V .. lOp 

250/2SV .. 14p 

500,'25V .. £0p 

8 - 8/450V 18p 

8- 18/450 V SOp 

16 + 1B/460Y 25p 

32- 32/350 V 2Sp 
SUB-MIN. ELECTROLYTICS. 1, 2, 4, 6, 8, IB, 25, 30, 50, 100, 
200mF 15V lOp; 500, lOOOmF 12V 18p; 20OOmF 25V 35p. 
CERAMIC lpF to 01 mP, 4p. Silver Mies 2 to SOOOpF, 4p- 
PAPER 350Y-01 4p. 5 13p; lmF 15p; 2mF 150V IS a. 
500V-0 001 to 005 4p: 1 5p: 25 Sp; 47 25v. 
LOOOV-tl 001, 0022, 0047. 01, 02, Sp; 047, 1, 14p. 
SILVER MICA. Close tolerance 1% 2 2-500pF Sp; 500-2 200 
pF lOp; 2,700-5,600pF SOp: 8,800pF-0 01, mid 30p; each. 
TWIN OANG. "0-0" 208pF i 176pP. 65p; Slow motion drive 
885 4-365 with 25 25 pF, 55 p; 500pF alow morion, standard 
45p ; small 3-gang 500pF £1 10. SHORT WAVE. Single 25pF 55p 
CHROME TELESCOPIC AERIAL, swivel base, 23in. 20p. 
TUNING. Solid dielectric. lOOpF. 500pF, 35p each. 
TRIMMERS. Compression 30, 50. 70pF, Gp; lOOpF, lfiOpF, 
Sp; 250pF, ISp; SOOpF, 750pF 10p; 1000 pF lOp, 
RECTIFTERS CONTACT COOLED 1 wave BOmA 8Sp; 
85mA 4Sp. SILICON BYZ13 30p ; BY100 SOp. 
Full wave Bridge Rectifiers 75mA SOp; 150mA 68p. 
EX-GOVERNMENT RECTIFIERS 250v, 200mA, 30p. 
NEON PANEL INDICATORS 250V AC/DC Red or Amber 20p. 
RESISTORS. Preferred values, 10 ohms to 10 meg. 
t w„ i w.„ 20% lp; 2 w. Sp. 

HIGH STABILITY, | w. 2% 10 ohms to 10 meg., lOp. 
Ditto 5% Preferred values 10 ohms to 10 meg., 4p. 
WIRE-WOUND RESISTORS 5 watt, 10 watt, IB watt, 
10 ohms to 100K, lOp each; 2-j watt, 1 ohm to 8 2 ohms lOp. 

Q MAX CHASSIS CUTTER 

Complete : a die, a punch, an Allen screw and key 
Jin. S3p iin. 88p liin. SSp ltin. £1-80 2^in.£2-£l 
Ein.83p lln. SSp liin. £1-03 1 Jin. £1-45 2ttn. £2-8« 
Jin. Sip lArln. SSp liin, £108 2in. £199 lin.sq.£l-B3 



AM- 



■FMVHF TUNING GANG 

Super guality small size l.j :■ l.| ■-: 
liln.. plus spindle li'^ iin. 385 + 
365 pF with 85 + 25 pF. British 
made. Geared slow motion drive 
8:1. Plastic dost cover. 6BA tapped 
Iron! vxing. Cast aluminium Irame 
Post Free 




50p 



25p each 
250-0-280 50 mA, 8 3 v. 2 amps, centre tapped . . £1-10 

250-0-250 80 mA. 6 3 v. 4 amp £140 

250-0-250 SO mA. 6 3 v. 3 5 a. S-S v. 1 a. or 5 v. 2 a. £2-00 
350-0-350 SO mA. 8 3 v. 3 5 a. 6-3 v. 1 a. or 5 v. 2 a, £200 
300-0-300 v. 120 mA., 6 3 v. 4 a. C.T. ; 6.3 v. 2 a. £2 50 
MINIATURE 200 v. 20mA. , S 8 v, 1 *, 21 x2i x Sin, 75p 
MIDGET 220 v. 45 ma,, 6-3 v. E a. 2( x2} xgin. SOp 

HEATER TRANS. 6 3v. 1, a 70p 

Ditto tapped see. 1.4 v., 2, 8, 4, 5, 6 3 v. 1 1 amp, . . SOp 
GENERAL PURPOSE LOW VOLTAGE. Tapped Outputs 
3, 4, 5, 8. 8, 9, 10, 12, 16, IS, £4 and 30 v. at 2 amp. £2-00 
1 amp., 8. 8, 10. 12, 18, 18, 20, 24, 30, 38, 40, 48, 60, £2 00 
AUTO TRANSFORMERS 0-115-230 ?. Input/Output, 
160w, £200; 600w, £5: lOOOw. £12. 
CHARGER TRANSFORMERS, Input 200/250v. 
lur S or 12v., 1| amp., £1-20; 4 amp. £1 SO. 
FULL WAVE BRIDGE CHARGER RECTIFIERS: 
8 or 12 v. outputs, II amp. 40p; 2 amp. SSp; 4 amp. SSp. 




E.M I. 13| x8in. 
LOUDSPEAKERS 

With flared tweeter cone and ceramic 
magnet. IS watts. /•». •> r> 

Bass res. 45-60 cps. T.A £3 

Flat 10,000 gauss. -"■•*■■*■ 

State 3 or 8 or 15 ohm. Post 16p each 

Also with twin tweeters. 

With crossover, 10 watt. 

State 3 or S or 15 ohm. Post 15p each 

Recommended Teak Cabinet 
Size 18 x 10 x Sin. Post 25p 



£4 



£5 




200/250 
v. A.C. 
Leaflet 
S.A.E. 



I0W MINI-MODULE £3 25 
LOUDSPEAKER KIT **'„, 

Triple speaker system combining on ready cut bailie, 
t In, chipboard 15 in, X 8i In, Separate Baas, Middle 
and Treble loudspeakers and crossover condenser. The 
heavy duty 5 in. Bass Woofer unit ha* a low resonance 
cone. The mid-Range unit is specially designed to add 
drive to the middle register and the tweeter recreates the 
top end of the musical spectrum. Total response 
20-16,000 cps. Full instructions lor 3 or 15 ohm. 
TEAK VENEERED BOOKSHELF ENCLOSURE. 
18J X. 10t X Sin. Modern Design, 
dark grey Tygan covered baffle 



£5 



Post 25p 



ALL MODELS "BAKER SPEAKERS" IN STOCK 



BAKER I lin. MAJOR £9 




30-14,500 e.p.s„ l£in. 
double cone, wooter and 
tweeter cone together 
with a BAKER ceramic 
magnet assembly having 
a fini density o! 14,000 
gauss and a total nm ot 
145,000 Maxwells. Bass 
resonance 40 c.p.s. Rated 
20 watts. Voioe coils 
3 or 8 or 15 ohms. Post Free 



Module kit, 30-17.0OO c.p.s. 
with tweeter, crossover, 
baffle and 
instructions. 



£11.50 



BAKER "BIG — SOUND" SPEAKERS 

'Group 25' 'Group 35' 'Group 50' 

12 inch (-1 12 inch /n 15 irteh / I A 

26 watt *•' 35 watt •-' 50 watt *- ■ ~ 

3 or 8 ur 15 ohm 3 or 3 or 15 ohm 8 or 16 ohm 



TEAK HI-FI SPEAKER CABINETS, Fluted wood front 

For ISin. round Loudspeaker £9, Post SSp 

Por 13 x Bin. Loudspeaker £5. Post 25 p 

For 10 x Sin. round Loudspeaker £4, Post 25 p 

LOUDSPEAKER CABINET WADDING ISin. wide, 15p It, 



THIS EL AC CONE TWEETER IS OF THE VERT 
LATEST DESIGN AND GIVES A HIGHER 
STANDARD OF PERFORMANCE THAN 
MORE EXPENSIVE UNITS. 

The moving coil diaphragm gives a good 
radiation pattern to the higher frequencies 
and a smooth extension of total response 
lrom 1.000 cps to 18,000 cps. Size Sj x 
3} x &n. deep. Rating 10 watts. 3 ohm or 
15 ohm models. £ | t}Q Po „ lnj( 

TWO-WAY XOVER NETWORK 3000 c/s 

With variable tweeter attenuator giving sec orate high/low 
frequency balance. Mounted on panel 5 tin. X 4in. with 
control knob, tweeter and woofer leads and / I Of} Post 




input terminals. Suitable for 3 to 8 ohm imp. 



lOp 



Horn Tweeters 2-16kc/s, 10W S ohm or 16 ohm £1 50. 
De Luxe Horn Tweeters 2-18 Kc/s, 15 W. S ohm £3. 
TWO-WAY 3000cps CROSSOVERS 8 or 8 or 16 ohm 95p. 
SPECIAL OFFER! SO ohm, 2 !in., 2!in. dia. : 35 ohm. 3io. 
25ohm,3in. dia. ; 6 x 41n. ; 8 x Bin. Qflrt EACH 

15 ohm 3iin. dia; 7 x 4in.;8 x Sin. 7 "P TYPE 

8 ohm, 6 x 4ln„ S ohm, 21io, Sin, Sin. i x iin. 7 x 41n. 
LOUDSPEAKERS P.M. 3 OHMS. 6 Sin. £1.10; 8 x Sin. £1-25; 
8 x 2 lin. flop; Sin. £1.75: 10 x Sin. £1.90. 
Sin. WOOFER 8 watts mai. 20-10,000 cps. 8 or IS ohm. £1 80. 
ELAC 8 in. De Luxe Ceramic S ohm or 16 ohm £2 50. 
RICHARD ALLAN TWIN CONE LOUDSPEAKERS. 
Sin. dia. 4 watt; lOin. dia, 6 watt; 12in. dia. 6 watt 

3 or 8 or 15 ohm models £1.05 each. Post 15p. 
OUTPUT TRANS. EL34 etc. 2Sp; MIKE TRANS. 50:1 25p. 
SPEAKER COVERING MATERIALS. Samples Large S.A.E. 
GOODMAN'S OUTPUT TRANSFORMER 4 watt push-pull 
lor valves ELS4 etc., 3, S and 15 ohms B5p, Post 20p, 

100 WATT HIGH POWER P.A. AMPLIFIER 

4 inputs speech and music. Response 10-30,000 cps 
Hatches all loudspeakers. Weight only 12 lb. flf* Posl 
A.C. mains 200/250 V. Details S.A.E. fcJW Free 



ALL EAGLE PRODUCTS 

SUPPLIED AT LOWEST PRICES 

ILLUSTHATED EAGLE CATALOGUE 25p. Post Free, 



£4 



BARGAIN AM TUNER. Mediom Wave. 
Transistor Superset. Ferrite aerial. volt. 

BARGAIN 4 CHANNEL TRANSISTOR MIXER 

Add musical highlights and sound e fleets to recordings. 
Will mis Microphone, records, tape and tuner / 7 

with separate controls into single output. 9 volt. *" J 



BARGAIN FM TUNER SS-10S Mc/S Six Transistor. 8 volt 
Printed Circuit. Calibrated slide dial toning, £ I Q 

Wainnt Cabinet. Size 7 x 5 x 4inch fclu 

BARGAIN m TUNER a. above leas cabinet £7.50 

FH STEREO MULTIPLEX ADAPTOR. For above or 
general use. Ready made with 4 transistors, fC 

k AinAcm *— 1 



BARGAIN 3 WATT AMPLIFEIR. 4 Transistor /■> Cfl 
Push-Full Ready built, with volume control. 8v. «i J «*V 



COAXIAL PLUG Sp. PANEL SOCKETS Op. ^JNE ISp. 
OUTLET HOXES. SURFACE OR FLUSH 25p. 
BALANCED TWIN FEEDERS 5p yd, 80 ohms or 300 ohms. 
JACK SOCKET Std. open-circnit 14p, closed circuit SSp; 
Chrome Lead Socket SSp. Phono Plugs Sp, Phone Socket 5p. 
JACK PLUGS Std. Chrome ISp: 3-5mm Chrome 14p. DIN 
SOCKETS Chassis 3-pln lOp; 5-pin lOp. DIN SOCKETS Lead 
3-pin 18p; 5-pin 25p. DIN PLUGS 3- pin ISp; 5-pin 25p. 
VALVE HOLDERS, Sp; CERAMIC 8p; CANS 5p. 



SPECIALISTS 






E.M.I. TAPE MOTORS 

120v. or 240v. AC. 1300 r.p.m. 4 pole 
135mA, Spindle 0187x0 75in. 
Size Six 2s x2iin. (Illustrated). f\ 1C 
Post ISp, *■•** 
BALFOUR GRAM MOTORS 
r-k -ii; | «JEaBBV*v 120v. or 240v, A.C. 1,200 r.p.m. 4 pole 

gg ^ RADIO B00KS-.LIST S.A.E. ^ T*n*Z%J. * z To«X «5p 

RETURN OF POn DESPATCH, HI-FI STOCKISTS. CUSTOMERS FREE CAR PARK. CALLERS WELCOME 

337 WH1TEHORSE ROAD, CROYDON 

Open 9-6 p.m, ( W««ln«te<lmys 9-1 p.m., Saturdays 9-5 p.m.) 

Tol. 0I-AB4-IM5 

997 



"THE INSTANT 
BULK TAPE 
ERASER AND 
RECORDING 
HEAD 
DEMAGNETISES 

Minimum Post and Pocking 150 

RADIO COMPONENT 

L»t Sp. Written guarantee with every purchase. (Export- Remit cash afKj extra postage.) Buses 133, 68 pass door. S.R. Sw. Seihurst. 




There's only one way to buy 
stereo equipment. Listen to it. Lots of 
it. Until you find the sound you like 
for the money you've got. 

Sound advice. But try acting 
on if in 99% of hi-fi dealers and you'll 
be. asked to show the colour of your 
money. We at Roc think that's unfair, 
So we fitted out our store in the 
Edgware Road with a series of sound 
systems, so you can hear all the 
stereo you want until you find the 
equipment you ike. With no hustling. 



But if you're one of those poor 
unfortunates </vho cannot make it in 
person, well sell you a system by 
mail. We've got the best range"! n 
town f r om single speakers to 
complete stereo set-ups. 

Here sre just six of the 
systems we've got in stock, 

Fill in the coupon and we'll 
have our systems brochure back to 
you by return: 



998 




System I. 

Amplifier 

Output: 

Frequency Response: 

Inputs: 

Controls: 

Speakers: 
Capacity: 

Frequency Response: 
Turntable: 



System II. 

Amplifier 

Output: 

Frequency Response: 

Inputs: 

Controls: 

Speakers: 
Capacity: 

Frequency Response: 
Turntable: 



System III. 

Amplifier 

Output: 

Frequency Response: 

Inputs: 

Controls: 

Speakers: 

Turntable: 



Price: £39-90 

4 Watts per channel 
50-10000 Hz. 

Tuner, Ceramic Cartridge 
Volume, Tone & Balance 

6 Watts 

40-16000 Hz. 

Garrard 2025TC, Ceramic Cartridge, 

Base and Cover 

Matching AM/FM/FM Stereo Tuner 



Price: £49-90 

8 Watts per Channel 
40-18000 Hz. 

Tuner, Tape, Ceramic Cartridge 
Volume. Bass, Treble and Balance 

10 Warts 
40-19000 Hz. 
As system I. 



Price: (A) £59-90 (B) £69-90 

15 Watts per Channel 
30-18000 Hz. 

Tuner, Tape. Magnetic & Ceramic 
Volume, Bass, Treble and Balance 
As System II 

System I II A Garrard 2025TC, 
Ceramic Cartridge, Base and Cover 
System II IB Garrard SP.25 MK III, 
Magnetic Cartridge, Base and Cover 



System IV. 

Amplifier 

Output: 

Frequency Response: 

Inputs: 

Controls: 

Speakers: 
Capacity: 

Frequency Response: 
Turntable: 



Pnce: £79-90 

20 Watts per Channel 

25-20000 Hz. 

Tuner, Tape Magnetic & Ceramic Cartridge 

2 Volume, Bass. Treble and Loudness 

20 Watts 

35-20000 Hz. 



Garrard SP.25 MKHI, Magnetic Cartridge, 
Base and Cover 
Matching AF/FM/FM Stereo Tuner: £36-00 



System V. 

Tuner Amplifier- 
Output: 

Frequency Response: 
inputs. 
Controls: 
FM Sensitivity 
AM Sensitivity: 
Speakers: 
Capacity: 
Frequency Response: 

Turntable: 

System VI. 

Amplifier 

Output: 

Frequency Response: 

Inputs: 

Controls: 

Speakers: 
Capacity: 
Frequency Response: 

Turntable: 



Price: £11 5-00 

18 Watts per Channel 

30-20000 Hz. 

Tape & Magnetic Cartridge 

2 Volume, Bass, Treble and Tuning 

2-5 microvolts 

100 micro volts 

20 Warts . 
35-20000 Hz. 

As System IV 

Price: £182*00 

30 Watts per Channel 

20-30000 Hz. 

Auxilliary, Magnetic & Ceramic 

Cartridge 

Volume, Bass, Treble, Balance, 

Loudness and Monitor 

30 Watts 
35-20000 Hz. 

ThorensTD150AB Magnetic 
Cartridge, Base & Cover 



999 



This MONTH'S Best Buy . . 




8 



AKG K50 Dynamic 
Stereo headphones 

Complete with spare ear muffs, 
je£W-40f Price *™>'W p . &„. 



Available only from us at this price. Due to entire 
purchase of manufacturer's remaining stock this 
fantastic offer Is open only while stocks last. 
* High-fidelity reproduction due to broad frequency response (20-20. 000Hz) 
»J P^ S ^r"h lit '" cr c eas ? d s, «"?° effect * Headphones fit Ihe head gently 
and do not shift * Earpieces fit ears snugly (Cardanic suspension) * Tone 
quality superior to conventional loudspeakers. * Only expensive studio loud- 
speakers can match the reproduction quality ol the K50. * Music can be 
reproduced at concert hall volume (I), preserving the lower bass notes and 
brilliant treble tones without causing any strain to the listener. 




GARRARD SP2S 
mkll £11 50 pius sop 

** " ■ ■***» carriage 
Normal price £15 57 
Single record playing unit. 
Features include cue and pause 
and automatic pick-up return and 
switch of). 

Wired with mains cable and 5ft. 
twin screened stereo cable, 
5 pin din plug. 63p extra- 
AP75 Complete with base and 
coyer £25 plus 75p carriage. 




PLUGS? 

sJsL _ Kt3 53K9 
PaB 1 0rJ-Pi n Din .\m-sii/20 p 

Pack !0S 3-Pin Din . . . , 18 p 

Pack 135 x" Jack .. .. 25 p 

Pack 130 *" Jack Stereo . . 41 p 

Pack TQ3 Loudspeaker Plug . . 15j» 

Pack 100 Phono Plug .. ., 6p 

Pack 230 3-Pin Socket . . 23 a 

Pack 236 5-Pin Socket . . 30(1 

Pack 234 Loudspeaker Socket. . 30p 
Ready-made Leads 

3-pin to 3-pin Din .. .. 63p 

3-pfn to open end .. , . 53p 

5-pln to S-pin Din .. .. BOp 

5-pln to open end . . ., es p 

5-pin to 4 phpno plugs . . S3p 

Speaker lead Din to spade 12ft 
38p. Extension lead Din plug to 
socket 12ft. 6Sp 

All leads approx. 6ft. In length. 
Post free, by return. 




PLINTH & COVER £525 

Unbeatable Value p / os SQpp, &p 

Suitable for AT60; SP25; 3000; 2500; 3500. Superb 
nnlsh. Sptndte can be left In position with cover on. 
Cover of neutral smoke tint perspex. 
Also available tor AP75; SL99; SL75 £6-88 plus 
50 p carr. 



Replacement Stereo 
DIAMOND STYLI 



75p 



8TA 9TA 9TAHC 

GP91 ST4 ST9 

EV26 GC8 '"Keacli 

others on request p. Ap, 13p 

Countdown S PEAK ER 

Teak Cabinet 

insur 

a. carr. 38p 

A speaker of out- 
standing specifi- 
cations and tech- 
nical merit. Solid 
teak cabinet size: 14* x 10' x 6 . 
Originally designed for use with our 
Countdown stereo budget system 
but now available separately. 




EMI lOw matched 
loudspeaker set 450 

Our price £3.75 Inc. iSpp.Lp. 



:\-\s^v 



13±" x 8," etfiptical loud- 
speaker and Indepen- 
dent high frequency 
units with associated 
crossover network. Fre- 
quency range 55 to 
13000Hz. The cone of 
the bass unit has a sur- 
round designed for high 
travel giving freedom from distortion 
when operated at low frequencies. 
Also 350 KIT 20W 
Frequency range: .T^ Eft 

20 to 20,0O0Hi. 3L./.0U 

Normal price £13.50 plus 40p p A „ 
Also 150 KIT 10W £9 M plus 
3, 8 or 15 ohms a^fc.JU 4g p p & B 



SINCLAIR Project 60 

SA VE nearly £J Normal price £23-90 

Designed for building Into _ ._ P'"s 
plinths etc., complete with £1 9 50p 
two 230 Output stages Bff. 

It. Send S.A.E. for full technical brochure. 



(20 watt) and power supply ur 
SINCLAIR 2000 AMPLIFIER SAVE £6-30 Our price" 6X4.15 



Magnetic cartridges 

Diamond r- a -re 

atyti £4.75 

plus 13p p, t, p. 

Today's value £B. 

Stylus replacement 

can be carried out without removing 

cartridge. Futty guaranteed 




SONOTONE 
Cartridge ... 

(Fitted Diamond Styll) 
(Ceramic) list price £4 TO 
Sensitivity: CO CA 

9TAHC 55mV/cm/eec 3tt.3U 

rms minimum at 45° at plus 
1.000Hz measured on tip 
Decca SXL2057 p. A p. 



Ronette 105 Stereo cartridge (Sapphire ?b Diamond LP) £i.;5l3p,p.&p 



J. J. FRANCIS 

(WOOD GREEN) LTD 
123 ALEXANDRA ROAD, HORNSEY, 



LONDON, N.8. 



Tel: 01-888 1662 



PADGETTS RADIO STORES 

OLD TOWN HALL, LIVERSEDGE, Y0RKS 
TEL. HECKM0KDW1KE 4285 

40 OHLY. The much sought alter Sighting Oomputor Marie XIVA, For the model 
maker. Condition Good. £2,50j> (S0/-J Carriage 11-00 {£1) 

AMPLIFIER UNIT TYPE A 1418. Complete with 52* and 6V6GT valves 350/230 volt. 
50 cycle. Transformer, deai Condition, Untested. £1-25 p (25/-). Carriage 76np (15/-). 

AIB POSITION UfDICATO'lS. Contains Oears, Ball Races, Dimmer Units, Lamps, 
Four numbered counters, -.4 volt Motor etc. Great interest to the model makers. 
In good condition. 75pn (15/-) . Carriage 50 op (10/-). 

GROUND POSITION INDICATOR. Contains $4. volt lamp. Prisms Mirror, Gears. 
Could interest Hche»ls A mo.1ei maters. 75np (15/-). Carriage 75np (15/-). 

NEW BOXED UNIT TYPE 8197. Contains two Toggle D.P.S.T. switches, also one 
Press Toggle D.P.S.T. SLtte ;n Miniature, 500 Ohm. Pre-set Pota P.X TX switches etc 
SSnp (5/-). P. fc P. 22Jn P (4/8). 23-00 (£3) per do«n. Carriage paid. 

TOGGLE SWITCHES. Ex Units D.P.D.T. lOnp (2/-), D.P.S.T. Sap (1/-). S.P.S.T 
Spring Loaded lOnp (2/-). D.P.S.T. Press Button Spring Loaded lOnp dtf-1. P. * P' 
on any switch 4np (9df, Do; . Post Paid. 

G -P.O. BELAYS EX-UlfTTS. 400 Ohrna and BOO Ohms SOnp (10/-) per doz. P. * P , 
2fino (5/-), Sample Belay Snp (1/3). P. & P. 5np (1/-). 

HLYIATURE BRASS LAMP HOLDER. lOnp (3/->. P. & P. Snp. (1/-). SOnp (18/-) per 
doz. Post Paid. Base Board Type. 

RECLAIMED T.7. TUBES with 12 months Guarantee. 17' AW 43/80 £l-SOp (30/-). 
MW 43/09 tllSOp (30/-). AW 43/88 *200 (40/-). Carriage and Insurance oa any 
tsbe 11-00 (30/-). 

IS CHAKHEL COMPLETE UNTESTED T.V. SETS. *2.50p (30/-). Carriage and 
Insurance fl.SOp (30/-). 

SPEAKERS REMOVED ETGM T.V. SETS. All 3 Ohm and P.M. 6x4. ISnp (3/-). 
7 x4. £5p (6/-). 8 x2 r 25a p (6/-). Post on any Speaker SOnp (4/-). 

VALVE LIST— Ei Equipment 3 montm guarantee. Single valves. Post Snp (7d), 
over 3 valves P. & P. Paid. 



ARP12 

EB91 

EF85 

EBFSO 

ECC81 

ECC8-2 

ECL8Q 

EF50 

EP80 

EFS1 

EY86 



6np (1/-) 
4np (9d> 
15np (3/-) 
15np (3/-) 
ISnp (3/-> 
15np (3/-) 
10ns m-) 
Snp U/-) 
Snp (1/7) 
4np (9d) 
Siap (5/-) 



POCB4 

PCF80 

30P12 

30F5 

PCL84 

PCL82 

FCL83 

PL36 

PL81 

FY33 

PY81 



lOnp (2/-) 


PT83 


lOnp (2/-) 


PZ30 


25np (5/-) 


III 91 


ISnp (3/-) 


U251 


20op (4/-) 


6BW7 


20b p (4/-> 


eU4 


26np (S/-y 


6P2B 


25 up (6/-) 


2(1111 


tOap (4/-) 


20P1 


25np (5/-) 


20P3 


Snp (1/7) 


30P4 



Snp (1/7) 
S5np (5/-) 
25np (5/-) 
SSnp {5/-1 
lOnp (2/-) 
25 np (3/-) 
SSnp (&/-) 
ISnp (3/-) 
BSnp (S/-) 
15np (3/-) 
SSnp (5/-) 



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1000 




TRANSISTORISED FM TUNER 

6 TRANSISTOR 
HIGH QUALITY 
TUNER, SIZE 
ONLY 6x4x2iin. 
3 I.F. stages. 
Double tuned dis- 
criminator. Ample 
output to feed moat 
amplifiers. Operates on 9 \ battery. Coverage 
8B-108Mc/b. Ready built ready for use, Fan- 
tastic value for money. £6-371, P. & P. 12 ip. 
Stereo multiplex adaptors £4-671. 

AVO CT471A MULTIMETER 

Battery operated, fully transistorised. 

Sensitivity lOOmD/v. 

Measures AC/DC Voltages 12mV to l,200v. 

AC/DC Current 120.4 to 1.2 Amp. 

Resistance 12 ohm to 120 rati 

HF, VH~F, VHF Voltage witb multiplier 

4v to 40Ov up to 60 Mo/s, 40i»V to 4v up to 

1,000 Mc/s. 

Offered in perfect condition. 

£56 each, Carr. 50p. 

CRYSTAL CALIBRATORS NO. 10 

Small portable 
crystal controlled 
wave meter. Size 
7 x 7» x 4in. 
Frequency range 
500 Ke/e-10 Uc/a 
Cup to 30 Mc/s on 
harmonies). 
Calibrated dial. 
Power require- 
ments 300V. D.C. 
15mA and 12V 
D.C. 0.3 A. 

Excellent cond ition. £4-47j, Carr. 37jp. 

B.C. 221 FREQUENCY METERS 

latest release 125 KHz— 20 MHz. Excellent 
condition. Fully tested and checked and 
complete with calibrator charts. 
£27 50 each. Carr. 50p, 

AM/FM SIGNAL GENERATORS 

Oscillator Test No. 
2. A high quality 
precision Instru- 
ment made lor the 
ministry by A irmec. 
Frequency coverage 
20-80 Mc/s. AM 
CW/FM. Incor- 
porates precision dial, level meter, precision 
attenuator IfiV-lOOniV. Operation from 12 
volt D.C. or 0/110/200/350 volt A.C. Size 
13 X 8 r x Oln. Supplied In brand new con- 
dition complete witb all connectors fully 
tented. 845. Carr. £1, 

AVO CT.38 ELECTRONIC 
MULTIMETERS 

High quality 97 range instrument which 
measures A.C. and D.C. Voltage. Current. 
Resistance and Power Output Ranges D.C. 
volts 25OmV-10.0O0v. (10 niegQ -llOmegEJ 
input). D.C, current I0fiA-26 amps. Ohms, 
0-1,000 megfi A.C. volt 100mV.-'J5jV 
(with R.F. measuring head up to 260 Mc/s) 
A.C. current lQjiA-SG amps. Power output 
50 micro-watt s-5 watts. Operation 0/1 10/ 
200,'250V. A.C. Supplied in perfect condition 
complete with circuit lead and R.F. probe. 
£25. Carr. 75p. 






BUe 19 i 



13i 



ADMIRALTY 62B RECEIVERS 

High quality 10 valve 
receiver manufactured 
by Murphy. Coverage in 
6 bands 160-300 Kc/s, 
EGO Kc"s-1.5Mc/s; 3.8- 
30.5 Mc/8 I.F. 600/Kc/b. 
Incorporate* 2 R.F. and 
3 I.F. stages, bandpass 
filter, noise limiter, 
crystal controlled B.F.O. 
calibrator I.F. output, 
etc. Built-in speaker, 
output lor phones. Oper- 
ation 180/230 vol A.C. 
161n. Weight 1141b. 
Offered in good working condition. £22 50. 
Carr. £1.30. With circuit diagrams. Also 
available 1341 L.F. version of above, 15 Kc/s- 

700 Kc/s. £17-50. Carr. £1.60. 

TO-3 PORTABLE OSCILLOSCOPE 

3ln. tube, Y amp. Sensiti- 
vity 01 v p-p/CM. Band- 
width 1-5 cps-1-5 HHS> 
Input imp. 2 meg Ci 2J>pF 
X amp. sensitivity 9 v. 
p-p/CM. Bandwidth 1.5 c pa 
-SOOKHi. Input imp. 2 
meg Q 20pF. Time base. 
5 ranges 10 cps-300 KHs. 
Synchronisation. Internal/ 
external. Illuminated scale 140 X 215 X 330 
mm. Weight 15 1 lb, 220,240V, A.C. Supplied 
brand new with handbook. £37-60. Carr. 60p. 
60p. 

TQ-2 PORTABLE OSCILLOSCOPE 
A general purpose low 
cost economy oscilloscope 
tor everyday use. Y amp, 
JJiuidwidt.h 2CPS-1MHZ. 
Input Imp. 2 meg II 23 
P.F. Ulnmluated scale. 
2in. tube. 116 x 180 x 
230mm. Weight 81b. 
220/240 V a.c. Supplied 
brand new witb band- 
book. £82.50, Carr. 60p. 




l^aMMMMM 



MABO OMI TF142E DISTORTION FACTOR 
METERS. Excellent condition. Fully tested. 
£20. Carr. 75p. 



USED EXTENSIVELY BY INDUSTRY, GOVERNMENT DEPARTMENTS, 

EDUCATIONAL AUTHORITIES, ETC. 
• LOW COST • QUICK DELIVERY • OVER 200 RANGES IN STOCK 
• OTHER RANGES TO ORDER 



NEW "SEW 

CLEAR PLASTIC 

METERS 




TYPESW.100 
100 x80 mm. 



20V. D.C. . . £2B7i 

SOitA 13 471 60V. D.C. . . £2 871 

S0-O-50fiA 18 371 800V. D.C. £2 971 

100|uA £3-371 1 «np- D-C. £2 871 

1 0-0-1 OOuA £3-25 6 amp, D.C, £2871 

SOOfiA £8121 300V. A.C. £2871 

1mA £2871 VU Meter. . £3-76 



" DESIGNS! 

1 BAKELITE PANEL 
METERS 

TYPE S-80 

80 mm, 
square fronts 

50/aA £S-12J 



60-0-60^iA £2-97* 
IOOjjA .... £2871 
10O-O-1 00(li A £2 87 1 

500uA £2-881 

1mA £2 47* 

20V. D.C. £8471 



y 

50V. D.C . £2 471 
300V. D.C. £2*71 
1 amp. D.C. £2 471 
5 amp. D.C. £2*71 
300V. A.C. £2 62i 
VU Meter. . £3-871 



'SEW" CLEAR PLASTIC METERS 



Type MR.86P, 4±in. x 4$lh. fronts. 

60mA £260 

100m A £2-60 

600mA £2 60 

1 amp £280 

5 amp £2 60 

15 amp £2 80 



Pi 



BO^A £380 

B0-O-50^iA £3 10 

IOOuA £310 

100 -0-100 a A £3 10 

200fiA £2 871 

SOO^A £2 75 

500-0-500^ A £2 80 

1mA £260 

1-0-lniA .. £2 60 

5mA £2 60 

10mA £2-80 



D.I'. 



£280 
£2-60 
£260 
£2-60 
£2-80 
£2 80 
£260 



160V. D.C. 
300V. D.C. 
15V. A.C. . 
300V. A.C. 
S Meter 1mA £2-8 7 i 
VU Meter . . £3-80 
1 amp. A.C- £2 80 
5 amp. A.C* £2 60 
10 amp, A.C. *£2- 80 
20 amp. A.C. -£2-80 
30 amp. A.C.*£2 80 



Type MB.52P. Sim. muare lronts. 



50|uA £310 

50-G-SQ^tA £2-80 
IOOjjA .... £2 80 
100-0-100fiA £2-371 



500fiA 
1mA . . 
6mA .. 
10mA 

:>i!iuA 

100mA 
500 out. 
1 amp. 
5 amp. 



£2 26 
£2 00 
£2 00 
£2 00 
£2 00 
£200 
£200 
£2 00 
£2 00 



10V. D.C. . 
20V. D.C. . 
gnv. ],r. . 
300V. D.C. 
15V. AC. . 
300V. A.C. 
S Meter lis 
VU Meter . 
1 amp. A.C* £2 00 
5 amp. A.C* £2 00 
10 amp. A.C. *£2- 00 
20 amp. A.C.*£200 
30 amp. A.C.*£2-00 



£200 
£2 00 
£2 00 
£2 00 
£2 00 
£200 
iA£210 
£310 



Type MR.65P. 3|in. x 3,in. lronts. 

£210 

£210 
£210 



Typ« MB,34P. 1 21 32 In. square fronts. 

_^„^, -200!!. A .... £1371 

300mA .... £1371 

500mA .... £1-871 

750mA .... £1-371 

1 amp £1-371 

2 amp £1871 

5 amp £1871 

10 amp. . . £1-871 

3V. D.C. . . £1-S7i 

10V. D.C... £187 1 

10V. D.C... £1-871 

20V. DC... £1-371 

IO0V. D.C. £1 871 

150V. D.C. £1-87* 

300V. D.C. £1-871 

500V. D.C £1-871 

750V. D.C. 81871 

15V. A.C. £1-871 

50V. A.C... £1*871 

180V. A.C. £1871 

300V. A.C. £1-871 

600V. A.C. £1-871 
S Meter 1mA £1-60 

VU Meter.. ££.10 



60mA.' iS 7 ** 

60-0-^5 Oji A £1-871 

lOO^A £1-871 

100-u-100/iA£175 

200iiA £1-76 

SOOjuA £1 50 

5OO-O-50O M A £1 871 

1mA £1-871 

1-0-lmA . . £1-371 

2mA £1 871 

6mA £1371 

10mA . . 
20mA . . 
50mA .. 
100mA . . 
130mA . . 



£1371 
£l-37i 
£1371 
£1-371 
£1371 



Type MR.48P. 2in, square tronU. 



50uA 3-37J I 10V. DC 

5O-O-50fiA £B 76 [ 20V. D.C 

lOOfiA £2-75 

100-d~lU0nA£2 60 

200iuA £2 80 

500M £2-871 

600-0-500pA£B10 

1mA £2 10 

5mA £2 10 

10mA £210 

50mA £210 

lOOmA £210 

600mA £2 10 

1 amp £210 

amp. £210 

10 amp £210 

15 amp. . . £2 10 
20 amp. .. £210 
30 amp. . . £2 10 
50 amp. . . £2 871 
5V. D.C. .. £210 



£810 
£210 
£210 
£210 
£210 
£210 
£2-10 



50V. D.C. . 
150V. DC. 
300V. D.C. 
15V. A.C. 
50V. A.C.. 
150 V. A.C 
300V. A.C. 
500V. A.C 
9 Meter 1mA £2-371 
VU Meter. . £8-871 
50mA A.C. *£2-10 
100mA A.C*£210 
200mA A.C.*£210 
500mA A.C.*£2-10 
1 amp. A.C* £8-10 
5 amp. AC* £2 10 
10auip.A.C."£2-10 
20amp.A.C*£210 
30 amp. A.C. "£210 



^MOVING IRON- 
ALL OTHERS MOVING COIL 
Please add postage 



-,QuA £2-25 

S0-0-50jjA £210 

100(tA £2-10 

1 0U-O-1 0O^.A £1.871 

SOOjtA .... £1-871 

600jtA £1 60 

B0fH-50OijA£l-5O 

1mA £1-60 

5mA ...... £1 60 

10mA £1-50 

60mA .... £160 

100mA £1-50 

600mA £1 50 

I amp .... £1-60 



£1-60 
£160 
£160 
£150 
£150 
£150 
£150 



5 amp. 
10V. D.C. . 
20V. D.C. . 
50 V. D.C . 
300V. D.C, 

iev. a.c . 

300V. A.C. 

8 Meter 1mA £1-671 

VU Meter. . £2-25 

1 amp. A.C* £1 60 

I 5 amp. A.C* £1-50 

10 amp. A.C.*£l-60 

j 20amp.A-C*£l 60 

I 30 amp. A.C *£1- 60 




SguA. £3-50 

SOjjiA £2-371 

5O-O-60(tA £2-25 

lOOfiA £2 25 

100-0-lOOfiA £2-25 

SOOfiA £2 10 

1mA £175 

1-0-lniA , . £1-75 




"SEW" BAKELITE 
PANEL METERS 

Type ME.65. 3iin. square fronts. 

500mA £1-75 

1 amp £1 75 

5 amp. £1-75 

16 amp £1-76 

30 amp £1-76 

50 amp £176 

5V. D.C . . £1-75 
10V. D.C. . . £1 76 
20V. D.C. . . £1 75 
gov. D.C. . . £1 76 
150V. D.C. £1-75 
300 V. D.C £17S 
30V. A.C* £1-76 
50V. A.C* £1 76 
150V. A.C* £1 76 
300V. A.C* £1 75 
OOOinA A.C* £1-76 
1 amp. A.C* £1-75 
5 amp. A.C* £1 75 
lOainp. A.C*£l-75 

5mA £1-75 20 amp. A.C. *£1 75 

10mA H-75 30arap.A.C.*£l-76 

50mA £1-75 50 amp. A.C.*£l-76 

100mA £1-75 VU Meier.. £310 





TRANSISTORISED L.C.R. A.C. 

MEASURING BRIDGE 
__^_^^^^__ A new portable 

bridge offering ex- 
cellent range and 
aceuracy at low 
cost. Eauges: E. 
in-Ill megO 
6 Eaugea ±1% 
L.l u H - 111 
KEJTEY8 8 Ran- 
ges -2% ClOpF 
± lllOmFd, 8 
Ranges ±2%. TURNS RATIO 1:1/1000- 
1:11100, 8 Raogea ±1%. Bridge voltage at 
1,000 cpa. Operated lrom 9 volts. lOOfiA. 
Meter Indication. Attractive % tone metal 
eaee. Stee "| x 5 x Mln. £20. P. & P, 26p 

COSS0R 1049 DOUBLE BEAM 
OSCILLOSCOPES 

D.C coupled. Rand widtb lKc's. Perfect 
order. £25. Carr. £1-50. 

TE-20 RF SIGNAL GENERATOR 

Accurate wide range signal generator cover- 
ing 120 kc'B-260 
Mc/s ou 6 bands. 
Directly calibrated 
variable K.F. at- 
tenuator. Operation 
M0/SMV a,c. 
Brand new with In- 
struction. £16, 
1'. ft P. 371P. S.A.E. 
lor details. 

LELAND MODEL 27 BEAT FREQUENCT 
OSCILUTORS 

Frequency 0-20 Kc/s. on 2 ranges. Output 
5O0Q or Zkd. Operation 20O/25OV. A.C. 
Supplied in perfect order. £12-60. Carr. 60p. 

MARCONI TF8S5 VIDEO OSCILLATORS 

0-5 mc/s Sine SquareWave £4S. Carr, £1. 

LAFAYETTE TE-46 RESISTANCE 
CAPACITY ANALYSER 

2 pF-2000 mFd 
2 okma 200 meg- 
ohms. A] so checks 
impedance, turns 
ratio, insulation, 
200/250V. A.C. 
Brand Sew 
£17-50. 
Carr, 37 lp. 

ADVANCE TEST EQUIPMENT 

Brand new boxed in original sealed carton* 
VM78. TJHT MILLIVOLT METER, 
100 Ke,'s to 1,000 Mc/s. AC 10mV to 3v. 
DC- 1* raV to 3v, Current 0.01 uA It, 0.3 
mi. Resistance 1 ohm to 10 megohm. 

£125. 

TTIS TRANSISTOR TESTER. Full ran«e 
of facllitlea lor resting PXP or XPX tran- 
sigtors In or out of circuit. 
£37-50. Carriage oOp per Item. 

MARCONI TFI95M BEAT FREQUENCY 

OSCILLATORS 

0-40 kc's, £20, Carr. £150 





EDGWISE METERS 

Type PE.70. 3 17'32in. X 1 1532in, x 
2z in. deep. 

50;iA £3 00 

50-0-50^ £2-871 

100/iA £2-871 

]O0-O-lO0,uA£275 
200^A £2-75 



iOOjtA £2 60 

1mA £2-871 

300V. A.C £2-87| 
VU Meter. . £3-26 




SESD FOR HJ,TJSTRATED BROCHURE ON SEW PANEL METERS— DISCOUNTS 
FOR QUANTITIES 



POWER RHEOSTATS 



Our latent edition jriviiix full details of a 
cimprditwivi: rnn-- nf HI-FI EQUIP- 
1IEVT COMPONENTS, TEST EOIiIP- 
MENT and COMiiUMCvriOXS EQi:iP- 
1LE^T. FHEE DISCOUNT COUPONS 
VALUE 60p. (10/-> 248 pages, fully illustrated 
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High quality ceramic construction. Winding' embedded in 
enamel. Heavy duty brush wiper. Continuous rating- Wide ranee 
available ex-stock. Single hole Biing, Jin. dla. shafts. Bulk quantities 

25WATT. 10/25^60/100/250:500/ 1000:1500/2500 or 5000 ohms, 721p, P. & P. Tip. 

50WATT in ■■'' ' -'-'00 :•■■■ i. : iiui.iolinis,fHI8R.*F.7te, 

100 WATT, l.ti, 10:25 .'SO.'IOOj^BO/oOO/ 1000 ur 2500 ohms, £1-371 P. A ?■ Tip- 




1001 



SEMI-CONDUCTORS/ VALVES 

BRAND NEW & FULLY GUARANTEED 



TRANSISTORS 



IN914 

IX400I 

1X4002 

IX40O3 

IN4004 

1N4005 

IN4006 

1X4007 

IX414S 

1X5054 

2G301 

■2 GSO-2 

£0303 

2G306 

2U3G8 

soaea 

20371 

2G374 

■2G381 

2X696 

2X697 

2X698 

■2S7d6 

2X706 A 

•2X708 

2N914 

2N916 

2X918 

2X929 

•2X930 

2X1131 

•2X1132 

M130S 

2X1303 

2N1304 

■2N1305 

2X1306 

2X1307 

2X1308 

2X1309 

2N1711 

J X J 889 

2X1893 

2X2147 

2 X -21 60 

■2X2193 

2N2217 

2X2218 

'2N2219 

2X23H3 

2X2369 

2N2369A EOp 

2X2484 35p 

2N2613 8SP 

2N2648 50p 

2X2904 SOp 

2N2923 17p 

2X2924 17p I BCY42 

2X2925 Up "' 

2N2926G lSp 

2X2926Y 12p 

2N282S0 lSp 

2X3053 SSp 

2X3054 GOp 

2X3055 75p,BIH24 

■2N3391A SOp 1 BfllS 

2X3416 37p!flt*l!7 

2X3570 £1.25* BF 1 67 

2X3702 12p ' BFI73 
18p J3F180 
17p BF181 
16p , BF1B2 
88p BFl«4 
lBp BF185 

I7p i'ruu 

12p I't 19" 
12p "' 

s.v 

•jV, 

Sin 



?P 
8p 
Sp 
lOp 
tOp 
Up 
15p 
SOp 
7p 
22p 
SOp 
22p 
25p 
SOp 
3Dp 
20p 
22p 
B7p 

25p 

tft) 

17p 
42p 

Kb 

12p 
Iftp 

sap 

3S-V 

37; 
22 p 

a; j 

30p 



AC187 
AC168 
ACY17 
ACY18 
ACY19 
ACV20 
ACY21 
ACY22 
ACY28 
ACY40 
AD140 
AD 149 
AD 161 
AD 162 
AF114 
AF1I5 
AFH6 
AF1I7 
AF118 
AF119 
AF124 
AF126 
AF127 
AF139 
AF178 
AF180 
A Flit I 
AF166 
AF239 
ASY26 
A8Y27 
30p ABY23 
SOp I A8Z17 
88p J AUYlO 
25p BAYS1 
25s BC1Q7 

2Sp Boura 

S6p'BC109 

80p BC113 

" BC116 

BC125 

DC 126 

BC147 

BC148 

BC149 

BC167 

47p BC17-2 

40p BC177 

30p BC18H 

32p BC182L 

Up;BC184L 

20p I BC212L 

" BCY30 

BCY31 

BOYBa 

BCY33 

BCY34 

BCY38 



BCY43 
BCY7I 
BCY72 
HCZI1 
BD121 
Bill 23 



2X3703 

2X3704 

2X3705 

2X3706 

'2X3707 

2X3708 

2X3709 

2X3710 

2X3711 

2X3819 

■2X3903 

2X3904 

2X3905 

2X3906 

■2N4058 

■2X4059 

2X4061 

2X4062 

2X4286 

•2X4287 

2X4288 

2X4289 

2N4290 

'2X4291 

2X4292 

■2X5354 

2X5355 

B8102 

28103 

2S104 

40250 

40381 

40362 

AC107 

AC126 

AC127 

AC12S 

A CI 64 

AC176 



15p 
15p 

20l! 

40p 

Ltfjf: 
Mr 
2a? 
97 5 



BY 1-24 
BY 126 
BY 127 
BYZ10 
BYZ11 
UYZ12 
BYZ13 
MJ480 

MJ481 £125 

MPF1Q2 *2p 

MPF103 3Gp 

MPF104 S7p 

MFF105 40p 

XKT213 2«p 

NKT214 18p 

XKT218 37p 

XKT217 40p 

XKT224 88p 

XKT241 »7p 

XKT261 20p 

XKT271 8Sp 

SKX272 ]»p 

XKT274 20p 

XKT275 S5p 

HKT378 26p 

XKT281 87p 

XKT403 75p 

XKT404 S£p 



iZg XKT405 75p 



3 2 l! 

2,iD 
■i-in 
B7p 

■:» 

12]i 

:., i 

12p 
Sop 
•Slip 

COM. 

ivp 

iiOfi 
lip 
i?P 
:Vui. 

lOp 

I2 i( 
12p 

i5n 

sop 

oOp 
Sou 
HG). 
4 Op 
15p 
2 Op 
30p 
lop 
40o 
06P 
SOp 
SOii 
£5p 
47p 
25 p 
3:'r; 
SVn 



XKT773 B6p 
SKT10439 

37p 



OA5 

OAIO 

OA47 

OA70 

OA79 

OA81 

OA8S 

OA90 

0A91 

0AS5 

OA200 

OA292 

OA210 

OC19 

OC20 

0C22 

OC-23 

0C24 

OC25 

OC26 

0C28 

OC29 

OC35 

OC36 

0C41 

OC42 

0C44 

OC45 

OC46 

OC70 

0071 

OC72 

0073 

0074 

OC75 

OC76 

OC7T 

O078 

0C81 

OC81I> 

32p oess 

E6p I OC84 
SBp ' OC139 



BF200 
BF224 
BFSSS 

BF244 
BFX12 
BFX13 
BFX29 

f'.KXSO 

BFX44 

BFX85 

BFX56 

BFX87 

BFX88 

BFY18 

BFY20 

BFY50 

BFYS1 

BFY52 

BFY90 

BSX19 

BSX20 

B9X21 

B8X7B 

BSY26 

BHY27 

USY25 

LWY.-H 

B8Y39 

B3Y51 

B9Y66 

BBY95A lSp 

BY100 18p 



OC140 

OC169 

OC170 

0C171 

OC200 

OC201 

0C202 

0C2D3 

OC204 

0C205 

OC207 

OCF71 

0KF12 

OBP«0 

P346A 

PL4001 

PL4002 

!' U003 

PL4004 



22p PL4O05 
67p ™ 

17i; 

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37p 
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PL4006 
PL4007 
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07p 
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87p 
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17p 



5 + 
100 + 
500 + 
2X3055 
25 + 
100 + 



THYR1ST0RS 



25 = 
SOp 



100 
B7p 
37p 
65p 
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200 
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85p 
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300 350 

40p . — 

45p — 

70p — 



4011 
47p 
50p 
75p 
97p 



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6BE6 

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6BJ6 

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12A rti 

12AT7 
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12AX7 
18AV6 

12BA6 

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19AQ5 

20 Dl 

20K2 

20L1 

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25p 

25p 
27p 

sop 

45p 
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4-5p 

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VALVES 



30,: 

42p 

o&u 

Sun 

b>J. 

Tip 
85p 

70p 
92 p 
75p 
85p 
S0-> 
SOp 
SOn 

70 t ! 

93p 
30 p 
50;i 

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26Z5 
■25Z6 
30C1 6 
30CI7 
30C1S 
30 PS 
30FLI 
30FLI2 
30FLJ4 
30L15 
30L17 
SOP 1 2 
30P19 
30 PL! 
30PL13 
32pj30PL14 
40p i 35L0 
75p 38 \V4 
25 p 35 VA 
410p 35X5 
SOp 50B5 
67p (IKS 
80pl80 
8Sp|85A2 
3Sp 807 
37p 1623 
SOp | 5763 
2Sp|614fi 
30p AZ31 
B6pli'Y31 
SOplDAFOl 
4Sp|DAF90 
15p DF9I 
*0p DF9U 
86p DK91 
B5p]DK92 
Btp BK96 



tarn 

F.JI80 
EUS1 
GM84 
BM85 
I5M87 
KY51 
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EY87 
EZ40 
KZ41 

mm 

EZ8! 
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KT6G 
KT88 
Mill 4 



35p 
40p 
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35p 

£1-00 
4Sp 
40p 
40p 
48p 
45p 

45p 

esp 

28p 
4Sp 
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£1-70 
£175 
SOp 



f'lSi; 



4 Op i PC88 
45p FC97 



ro B 

C!5p 
33p 
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60p 
63p 

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30p 
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DL94 
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DM70 
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DY87 

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PABC80 40p 
BDp 

60 P 

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48p 
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GGp 

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35p 

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EABC80 35piPL82 
EAF42 SSp I PI.8S 

SOp PL64 

GGp PI^OO 

SOp ' PL504 



PO900 
PCC84 

rtxsn 

POC88 

POC89 

pcx; 189 
POP80 

PCF82 

PCFS4 

PCF86 

PCF800 

PC F 801 

PCF802 

PCF805 

PCFS06 

PCFS08 

PCL82 

PCL83 

PCM 4 

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PCL86 

PFL200 

PL36 

PL81 



34p 

50p 

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Bam 

EB(J41 
EBC8! 
EBF80 
J-'. 13 1-13 
EBF89 
ECL2I 
. EC86 
46p , EC88 
SGp i ECC40 



Mb 
Ma 

40p 

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Sip 
J5p 
U5p 

40p 
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B0084 

ECCSS 
ECC3-S 
I-liJFSO 
13CF82 
ECF80 
B0H91 
GCH35 
BCH42 
ECH81 
BCB83 
ECL80 
ECL82 
ECL83 
ECLSy 



Ml 

40p 
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80p 
BOp 

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3;mi 
85p 

57p 
3 Op 
70r 

3 Op 
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4 P 
35p 



50)1 

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75p 
70p 
75 1 

Bap 
85 1 
45li 
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45p 

m 

55p 
SOp 
45p 
MS 

4 On 
75r 
Sf : j 
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63m 

3 Op 
30,! 
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40p 
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75p 
75p 
BSp 
83; 
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40p 

40p 

£1-00 



87p|EF37 

Ms tons 



M!m, 
5Gp 
£1'10 
30p 
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SOp 
SSp 
SGp 

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40p 
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EF4I3 

EF41 

BF42 

EF80 

EF85 

EF86 

EFS9 

EF91 

EF92 

:: ;■' i S3 

BC184 

SHOO 



4Sp : EL34 
75n tLsa 



JE1-10 

SOp 

GOp 

£1-10 

£1.90 



EL41 
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ELS I 
KL84 

KT.sr, 



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PY3J 

PY33 

PY80 

PYB1 

PY82 

PY83- 

PY88 

PY800 

PY801 

1125 

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U50 

052 

U191 

U281 

0282 

U301 

0801 

ITABC80 SSp 

(JAF42 55p 
BGp UBC41 
40p ri)i;-i 
GOp ; UBFSO 
40p I-UF99 

SOp ! i;cx84 

" TJOC85 
rt'Fsn 
DCH2t 
UCH42 
OCH81 
CCL82 
OCL83 
UF4I 
UF80 
I7FB5 
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17L41 
ITL84 
55p I V4 i 

S8p inrss 

G6p YRl05/30 38p 

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43p| 

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6Gp 

70p 
SGp 
SSp 
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SSp 
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SGp 
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GOp 

40p 
40p 
SGp 

49p 
40p 
SSp 

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70p 
SGp 
SSp 
SOp 



SEND SAE FOB, FULL LISTS! 
DISCOOITTS K>% on 12+ uny one type. 
15% on 25+ any irne type. 
Large qaamfty dlscotuits nil application. 
Pontage: Sanil- llon.luetorii 8|i; Vidves 15p. 

ZEHER DIODES 

'200R1T. (3.3 In 33v) lSp; l.Swatt (2.4 to 
400v) £0p: 4)1 watt (3.9 to 100l-> 85p. 



INTEGRATED CIRCUITS 

L900 40p: LOU 40p: L923 SOp; 1C-10 
£8-60: SL403 £B£G; MC180S £268; 
MC1304 £2-76: PA246 ££4S: CA3005 
£1-17: CA3011 74p: CA3032 £1-8S: 
FCH131 GOp: F0H16I SOp; FJH141 SSp; 
FJH171 25p; FJH181 SSp; FJH221 SGp 
FJB231 SSp: FJH241 SGp: FJH2B1 BGp; 
FJJl'21 60p; FJJ131 GOp: F.IJ-211 £1E6' 
FJY101 SGp 







M-fimmPM&tr 

SAVE UP TO 

33*3% OR MORE 
SEND SAE. FOR 
DISCOUNT PRICE LISTS 
AND PACKAGE OFFERS! 



GARRARD 



FULL CCB.BE1TT RAKaE OFFERED BRABD SEW AT FANTASTIC SAVtlTSt 

40 Mk II atereo £8 40 

202GT/C tttereo £BS7i 

3000 stereo £1C 50 

SP25 Mk III £I1-7S 

SL65B £14-87 ; 

Carriage 37^p eitra each item. 

TEAK PLIXTH8 & PERSI-EX COVERS 

1. For 8P25, 8L65, HF,m.,. 8000, MM I/O 
2020, 1000. £8 971. 

2. For AP75, SL75, 8L95. E5-97J,. 

3. For SP25 etc. to operate -rfth lid In place 
£5 97|. Carriage 37Jp ettta eaeli type. Full range of Garrard accessories available. 



8L72B 


£2697 


AJ'76 


£S0-97i 


81,75 


£2GB7i 


8I75B 


£80-75 


8I.9SB 


£40 97 


401 


££9-07 




SPECIAL OFFERS! 



Cari-ard 8P25 MK III fitted (toldrliig O800 GOLDRIXQ GL69/2 fltted Goldring 0800 

cartriasre s.ud wooden plinth and plaatie cartridge complete vrith. deluie bass and 

eorer. Ready wired. Total lift price £36. cover. Total list price £50.80. 
Carr. OUR fan Carr. 

sop price: 3C<jSI 50p 



price £22,50 



TELETON SPECIAL OFFER ! 




OS10T AM.'FM STESEO TOKEIl AMPLI- 
FIER WITH MATOHINO PAIR 8 A 1003 
SPEAKER SYSTEMS. Output 4 watts per 
channel. Excellent reception, IFC, built-in 
MPX. CcrfXTAL Input. Tota: List £60-26. 
OUR PRICE £89-96. Carr. 6::tp. 
Alao available with Garrard 20->5T/C Record 
Changer, Plinth, cover and stereo cartridge. 
Ready wired £46. Cart. £l-00. 



TAPE CASSETTES 

Top quality in plastic libnuy boxes. 
090 60 mln 42*p, 3 (or £1-:>21. 
C80 90 min 62ip, 3 for £1 -JiO. 
C120 120 min 76p. 3 !or £S:.7i. 
Cassette Head Cleaner 66p. Po.!t Extra. 



HOSIDEN OH04S 2- WAY STEREO 
HEADSETS 

Each beat Iph one con- 
tains a !:lin. woofer 
and a I n. tweeter. 
Bnllt In individual 
level controls. 8(1 Inip. 
35 -18,000c/ s with cable 
and stereo plug. £S.97t 
P. A P. UMj. 




TELETON SAO-206 
" AMPLIFIER 




Latest exulting rdca™. Branil" 
6 + S WKtts rrai. Inpiii.™' t,ir n«kg. xta), anx 
tape. Volume, baas, treble, slitting balance, 
scratch flltet and Loudness controls. Rec. 
List «29. OUR PRICE £18-87 Carr. 37p. 



b.s.r. Mcdonald 

MP 60 £1166 610 £16 66 

510 £13-95 310 £10-96 

Carriage 87lp extra each item 
TEAK BASE AHD PERSPEX COVER for 
above B8R range £3 97 r. Carriage 3"ip 
TPDI SERIES with plinth and cover and. 
ready wired. 

MF60 £19-50 610 £22 96 

510 £20 95 
Carriage GOp: extra each item 

GOODMANS 
SPECIAL OFFERS! 

MAX AMP 30 Stereo Amplifier 16 + 16 watt 
r.m.s. with matching 8TEREOMAX AM/FM 
Tuner. Total list price £136-52. 

OCR JOQQ THE PAIR 
PRICE »03 Carriage £1 

GOODMANS SPEAKERS I 

MEZZO IH, teak. 

OUR PRICE £86.60 pr. Carr. £1 
MAG BUM K2, teak. 

OUR PRICE £33-00 pr. Carr. £1 
MAMBO, teak. List £44-65 pr. 

OUR PRICE £38 SO pr. Carr. SOp 
MABTMBO 

OUR PRICE £3600 pr. Carr. «n P . 
MAGESTER, teak. Lint £57 each, 

OUR PRICE £37-871 each. Carr. £1 
Magfster stand £S87i extra 



TE-1 036 STEREO 
HEADPHONES 
Low cost high perform- 
ance stereo headphones. 
Foam rubber ear cups. 
Adjustable head-hand. 
S ohm impedance. 26- 
18,000 B.z. With lead and 
stereo jack plug. ONLY 
£187,. P. & P. l2 T p 




■1 x Z30 amplifj 

PV - 



1002 



*■ See previous page 



AMERICAN TA a E 
First grade quality American -;apes. Brand 
new. Discount on quantities. 

3in, 225ft, L.P. acetate 17Jp 

3J1I1- 600It. T.P. mylar SOp 

Sin. 600ft. std. plastic 42 lp 

tin, 900it. L.P. acetate SOp 

51n. l/200rt. D.P. mylar 76p 

6 Jin. 1,200ft. L,P. acetate 6SiP 

5 t ln. 1,200ft. L.P. mylar SOp 

5IIn. l.BOOft. D.P. mylar £1184 

Sfln. 2,400K. T.P. mylar £1 87 j 

7in. 1,200ft. std. acetate 08ip 

71a. 1,800ft, L.P. acetate 76p 

"in. l,8001t. L.P. mylar .,8100 

71n. 2,400(t. D.P. mylar £126 

7in, 3,600Jt, T.P. mylar £226 

Postage lOp. Over £3 post paid. 



SINCLAIR EQUIPMENT 

Project 60. Package offers. 

£39 amplifier, stereo 60 pre-amp, PZ5 
power supply. £18. Carr. 37fp. 
Or with FZ6 power supply £81. 
Carr. 37 lp. 2 x Z50 amplifier, 
stereo 60 pre-amp, FZ8 
power supply. £21-60. 
Carr. 37tp. 
Tr3jiHf.irn.ef .or PZ8, £8B7i extra. 
Add to any of the above £4-87 T (or active 
filter unit and £18 for a pair of Q16 speakers. 
Project 60 FM Tuner £20-87*. Carr. 37tp. 
Ail other Sinclair products In stock. 
2000 Amplifier £88-87} Carr. 37,p. 
3000 Amplifier £36. Carr, 37ip. 
Neoterio Amplifier £46.971: Carr. 37 t p. 

ECHO HS-606 STEREO HEADPHONES 
Wonderfully com- 
fortable. Light- 
weight adjustable 
vinyl headband. 
Oft. cable and 
stereo lack plug. 
25-17,000 OPS. 8 
ohm imp, £3.37 r 

p. a p. iaip. 




G.W. SMITH & Co. (RADIO) LTD. 



See opposite page * 



RUSSIAN C1-16 DOUBLE 
BEAM OSCILLOSCOPES 

6 MHz Pasa Band. Separate Tl, Y2 ampli- 
fiers. Calibrated triggered sweep from ■! sec 
to 100 mi 1 11 see/cm. 

Supplied complete with all accessories and 

in 9 tract iocs £87. Carr. paid. 




MARCONI 
T/44/TF956 

AF Absorption 

Wattmeter 

1 ft I watts to 6 watts, 

«30. Carr, El. 




UIH. DECADE 

RESISTANCE 

ATTENUATOR 

Variable range 0- 
llldB. Connections, 
Unbalanced T and 
Bridge T. Impedance 064 U range (O.ldB X 
10> + [ldU y. 101 -5-10+ 20 -f 30 + 4MB. 
l-Yenueney: d.c. to 200kilz (-3dB). Accur- 
acy: D.OodB. + Indication d£ X 0.01. 
Maximum Input less than 4W (50V). Built in 
flOO fi load resistance with internal/external 
switch. Brand new. £37-60. P. & P. 25p. 

" BELCO AF-5A 

SOLID STATE SINE SQUARE 
WAVE C.R. OSCILLATOR. 

Sine IS— '200.000 II*: Square IB— 50,000 Hz 
Output mil, — 10 dH (10 K ohms) 
Operation in- 
ternal batteries 
Attractive 2- 
tone ease 7|-* 
X 5" X 2". 
Price £17-60. 
Carr. 17 (p. 




IE-ISA Transistorised 
SiKnal Generator, riiaxiges 
4O0kW?.— SOmllz. an 
t nex pensl ve instruiuc tit 
for the handyman. 
Operates on 9v battery. 
Wide cany to read scale. 
^00 kill! modulation. 
5* XJ{K 3*in- 
Ootriolate with Instruc- 
tions and leads. £7 97*. 
P. 4 P. iOn. 






BELCO DA-20 SOLID STATE 
DECADE AUDIO OSCILLATOR 

New high quality port, 
able Instrument, Sine 
1 Itz to 100 KHz. 
Square 20 l£z to 20 KHz. 
Output max 1- 10 dB 
(10 K ohms). Opera- 
tion 220/240v. A.C. 
Size 215inm x IS in in x 
120mm. 
Price £27 60. Carr. 25 p. 

TE-40 HIGH SENSITIVITY 
AC. VOLTMETER 

[0 meg. Input 10 ranges: 
Ol/-0OSrl/-3/ 1 IS! 10/30/ I0O; 
300 V. R.H.9. 4cps.-l-2 Me js. 
Decibels -40 to -J-SOdil. 
Supplied brand new complete 
with leads and instructlon*. 
Operation 230V. A.C. £17-80. 
Carr. 25p. 

TE-65 VALVE VOLTMETER 

High quality instrument 
■with 28 ranges. D.C. volts 
1-6-1,'OOv. AC. volts 
1-5 — l,600v. Keslatance 
up to 1,000 megohms. 
200/240 v. A.C. operation. 
Complete with probe and 
instructions. 
£17-60. P. & P. 30p. 
Additional probes avail- 
able: R.F. £2-121: H.V. 
£B50. 

AUTO TRANSFORMERS 

0/I15/230V. 9tep up or step down. Fully 
shrouded. 

150 W. £U-37i P. & P. 171P 

300 W. S3-85 P. A P. 22}n 

500 w. £4 97^ P. & P. S9Jp 

1000 W. £7-25 P. * P. S~ip 

1300 W. £8 B7t P. & P. 42jp 

SOLID STATE VARIABLE A.C 
VOLTAGE REGULATORS 

Compact and panel 
mounting. Ideal for con* 
irol ot lamps, drills, 
electrical appliances etc. 
Input 230/240v. A.C. 
Output continuously 

variable from 20 v — 230 v. 
Model MB 2305 S amp 
68 x 46 it 43mm £8 37i. 
Modi'] illl 2310 10 limp 
90 x «8 x 60mm 81107^. 
Postage 12|p, 



MULTIMETERS for £V6W purposel 



TECH PT-S4. 1,000 
O.P.V. 0/10/50/250/ 
'lOOA.OOOV, A.C. and 
D.C, 0/1 /1 00/ 500mA. 
D.C. 0/100K. £1-871. 
P. A P. 12tp. 



HON0B TB.10A, aukll/Vuit 
5/2S 50 250/500/2,500 v, D.C. 
10/5 0/100/ 5 00/ 1,000 v. A.C. 
0/50nA,2.SmA/250mA D.C. 
0/6K/6 meg. ohm. —20 to 
+ 22 dE. 10-0, 100 mid. 
0. 100-0.1 mfd. £3 47 J. 
P. & P. lop. 



MODEL TE-200 20,000 O.P.V. 
Mirror scale, overload protec* 
timi. o;25.'12r>.-i,(KiO v.D.U. 
i .• :::,■• :,000 Y.A.C, 9?e0 
uA/2oO mA. 0/60K/6 meefi. 
-20 to +62 tlb. £3-76. 
P. « P. lap. 




MODEL 500 30,000 O.P.V. 
with overload protection, 
mirror scale 0/5/2-5/10/25/ 
100/2DO/500/i,OOOv. D.C. 
1/2-5/10/25/ 100/250/500/ 
l.OOOv. A.C. O/SOjlA/5/50/ 
."iOOiiiA. 12 amp. D.C. 
O/OOK/6 Mest./flO MegQ, 
£8 87;. Post paid. 



MODEL TE-300. 30,000 
O.P.V. Mirror scale, overload 
protection /. H i Si 1 5 . It ,'300 1 
1,200V. D.C. 0/6/30/12!l:'M0ii/ 
1,200V. A.C. 0/30uA/0rnA/ 
i)OmA/300mA/600mA. 0/8K/ 
80K/800K/S meg. ohm - 20 to 
+ 63 db. ii 97 S- P. & F. ISp. 



MODEL TE-80. 20,000 
it. P. v. ii/nj/oO/iori/siMi/ 
l.OOOv A.C. 0/5/26/50/250/ 
500/1,000 v. D.C. 0-^50uA. 
5/50/oOOmA. 0/6K/60K/ 
GOOK/6rnog, £4-871. 
P. *P. 16p. 





MODEL TE-70. 30,000 
O.P.V. 3/15 ! 60 -'300/ 600/ 
l,200v. D.C. 0,'e<30.']20;SOO' 
I .BOO v. A.C, u/9&nA/3/3ty 

300mA. 0/16K/ Kin K /I.BM/] rt 
MegQ. £6-60. P. & P. 15p. 



MODEL TE-90 50,000 
O.P.V. Mirror scale, overload 
protection. 0/3,'12/60,'300/eOO 
1,200 v. D.C. 0/8/30/120/300, 
1.200 v. D.C. .0S,'8.<Wu00mA. 
D.C. 16K/180K/l,6,16MBiTn. 
-20 to +63 db, £7-60. 
T. & P. 15p. 





THE MODEL TW-50K 46 
ranges, mirror scale. 50 K /Vol. 
D.C, 5K /Volt A.C. D.C: 
Volts .125. .25, 1.26, 2.5, 5, 10. 
25, 60. 125, 250, 600. 1000V, 
VC, Volts: 1.5, 3, 5. 10, 25. 
30, 125. 250, 600. InOOV. D.C. 
CuiTent: 25, oOuA, 2.S, 5. 25, 
50, 260, 50OmA, 6, 10 amp. 
Restetanoe: 10K, 100K, 1 MEG, 
' 10 MEOQ, Decibels: -20 to + 
5 dB. £8-87i. P. A P. 17ip. 




TE-S00 20.000 VOLT 
GIANT MULTIMETER. 
Mirror scale and overload 
protection. 6in. full view 
meter, 2 colour scale. 0/2.5/ 
1 0/260/ J. 000/5.000 v. A.C. 
n/26/12.5/10/50/250/1,000/ 
.-..000 v. D.C. 0/60HA/110/ 
lOO/SOOmA/10 amp. D.C. 
U2K.200K/20 MEO, OHM, 
£15. P. * P. 23p. 



TMK MODEL TW-20CB FEA- 
TURES BESETTABLE 0VEB- 
LOAD BUTTOH. Sensitivity - 
aOKfi/Volt D.C. HKn/Voll 
A.C. D.C. Volts: 0-0.6, 2.5, 10. 
00, 250, 1,000V. A.C. Volts: 
0-2.5, 10. 50, 250, 1.000V, D.C. 
Currents: 0-4.05, 0.5, 6, 50. 
000mA. Resistance: 0-5 K, 50K. 
0-5O0K. 5 MEGQ. Dcr-ibel-: 
-20 to -i-B2 db. £11-50. P. & P. 
17Jp. 



MODEL AS-100D. 100KQ/ 
Volt. 5in., mirror scale. Built- 
in meter protection 0/3/12/60/ 
120/3 00/600/ 1, 200 v. D.C, 
0. '6/30 ,'120/ 300/600 v. A.C. 
10uA;i} ; 'fiO/300MA 12 Amp. 
0:2K 200K-2M '200MQ. -20 
to +17 bB. £12-50. P. & P. 

mp. 




MODEL 6025. 57 Ranges. 
Giant 5iin, Meter. Pol- 
arity Reverse Switch. 
Sensitivity; 50K /Volt 
D.C. 5K /Volt A.C. D.C. 
Volt-;: .125. .25, 1.25, 5, 
10, 25, 50, 125, 250, 500, 
1,000V. A.C. Volts: 1.5, 
:!. 5, 10, 25. 50, 125, 250. 
500, 1,000V. D.C. Cur- 
tenl: 25, 50uA, 2.5. 5, 

25. 80, 250, BOOmA, 5, 10 amp. Reals- 

tauce:2 K.10K. 100K, 1MEO, 10MROQ. 

Decibels: -20 to +85 db. £1260. P. & P. 

1TJ,' 





MODEL TE-12 
20,000 O.P.V. 0/0.6/6/30/120/ 
i :00/1, 200/3,000/6, OOOv. D.C 
li/fl/30/12O/6O0/l,200v. A.O i 
i'6OftA/6/6O/aO0mA. 0/0K/ 
':00K/aMeg./60 Meg. Q 50pP 
i-.2mPd. £597J. P. & P. 17lp 



FTC-401 TRANSISTOR TESTER 



Full capabUIBes for mea- 
suring A, B and 100. 
XPN or PNP. Equally 
adaptable tor cheeking 
diodes. Supplied com- 
plete with instructions, 
battery and leads. 
£687*. P- & P. ISp. 




TMK LAB TESTER. 
100.000 O.P.V, OJin. 
Scale Buzzer Short Cir- 
cuit Check. Sensitivity: 
100.000 O.P.V. D.C- 5K 
Q'Volt A.C. D.C. Volts: 
,5, 2.5, 10, 50, 250, ],0()0 
V. A.C. Volts: 3, 10, 50, 
60, 230, 500. 1.000V. 
D.C. Cm-rent: 10, lOOuA, 
10, 100, 500mA, 2.5, 10 
amp. Resistance: IK, 10K. I00K. 10MEG, 
100 MEGQ. Decibels: -10 to 49 db. Plas- 
tic Case with Can-vine Handle. Size 7iiu. 
i 83 in. i 31 In. £18-80. P. & P. 25p. 





SKYWO0D SW-SOO 
50K[)/Volt. Mirror 
scale DC Volts 
0.0/3/12/30/300/600, 
DC Current 2CtnA/6/ 
AOOiiiA Resistance 
10K/100K/1 Meg/10 
Meg. Decibels — 20 
to +57 db. «7S0. 
P. & P. 15p. 



270° WIDE AHGLE 

1mA METERS 

MW1-6 60mm square 

£3-97 J 
MW1-8 80mm square 

£4-B7i 
P. & P. extra 






■■YAMABISH1" VARIABLE 
VOLTAGE TRANSFORMERS 

Excellent quality . Low price . Immediate delivery 



MODEL S-260 

General Purpose 

Beach Mounting 

1 Amp £5 50 

2.5 Amp £8-75 

5 Amp £9 75 

% Amp £14-50 

10 Amp £18-50 

12 Amp £21-00 

20 Amp £37 00 



MODEL S-260 B 

Panel Mounting 

1 Amp £5-50 

2.5 Amp £«-02t 

Please add postage 

ALL MODELS 

INPUT 230 VOLTS, 

50/80 CYCLES. 

OUTPUT VARIABLE 

0-260 VOLTS. 

Special discounts for qirinTi: j 



G.W.SMITH&C0.( 




tTHR-30 RECEIVER 

4 Bauds covering 55Qtce/9-30me/K. B.F.O, 
Built-in. Speaker 220,'240v. A.C. Urand new 
with instructions. £15-75. Carr. 37fti. 

WSS2 TRAFCEIVERS 

Large quantity available for EXPORT 1 

Excellent condition. Enquiries invited. 




UR-1A SOLID STATE C0MMUNICAT10M 

RECEIVER 

1 Bands covering 550kc/s-3Omc/s. FET, 

S Meter, Variable BFO lor SSB, Huilt-ln 

Speaker, Bandspread. Sensitivity Contrnl, 

220/240 v. A.C. or 12v. D.C. 121" X 4|- i 7". 

Brand newwith instructions. £25, Carr. 37Jp. 



LAFAYETTE HA-600 SOLID STATE 
RECREIVE 

General coverage 
150-400kc/s, 560 
kc/s-SOmc/s. FBT 
iront. end. 2 mcch, 
filters, product 
iletector, variable 
li.F.O,, noise limi- 
Ler, S. Meter, Bandspread. RF Gam. 16* I 
8|" X 81". IS lbs. 220/240V. AC. or 12v. D.C 
Brand new with instructions. £45. Carr. 50p. 





LAFAYETTE 

HA-S00 

SOLID STATE 

AMATEUR 

COMMUNICATIOH 

RECEIVER 



3.5-4, 7-7.3, 14-14.35, 21-21.45, 28-20. 7 
50-54 nie/s. Dual conversion, 2 n-.ech. 
flltere, product detector, variable BPO, S 
Meter, lOOkc/s calibrator. 220/240 v. A.C. or 
12v. D.C, 15* i Sj* i 81* 18 lbs. Brand new 
with Instructions, £57 50, Carr, Paid, 
(I00 fcc/a Crystal £1 B7& extra.) 

FULL RANGE OF TRIO 
EQUIPMENT IN STOCK 




CLASS D WAVEMETERS 

V crystal controlled hetero- 
dyne frequency meter 
■ overing 1-7-8 Me/a, 
Operation on 6 volts D.C. 

Ideal for amateur urn. 

tradable in good used con* 
ilrt ton. £6-97(- Carr. 37*p, 
Or brand new £7-97(. 
Carr. 37jp. 

VOLTAOE STABILISER TRANSFORMERS 
J80— 260v. input . Output 230v, AvaQablc 
150w or 225w. £12-50. Carr. 2Bp J _^ 

EDDYSTOHEVHF RECEIVERS Model 770 It 
19_16fi Mc/s, Excellent condition. £150 

TRANSISTORISED 
TWO-WAY 

TELEPHONE 
INTERCOM 

Operative over amazing' 
Ion; distances. Separate ca. 
and press to talk bntton- 
2-wire connection, 1000's n 
applications. Beautifully Qii 
Ished to ebony. Supplied 
complete witb batteries and 
wall brackets. 
£6-971. P- * F. 171P. 

INTERCOM/ BABY SITTER 

Transistorised In- 
conkfl, ideal tor 
home / ofltee I vrork- 
shop,, etc. 2-w*y 
buzzer CHlL system. 
Pot desk or wall 
mounting. Supplied 
complete witli con* 
ittn :c-k r wjre, bat* 
terie*. msiructjutifl* 2 atation £S-BT(. F- & P 
1-21V A nation £6 62*. P. A P. "J5p. 




W<0 



)LTD 



27 TOTTENHAM CT. RD. LONDON, W.I 
3 LISLE STREET, LONDON, W.C.2 
34 LISLE STREET, LONDON, W.C.2 
311 EDGWARE ROAD, LONDON, W.2 

OPEN 9-6 MONDAY TO SATURDAY < EDGWARE ROAD 



Tel: 01-636 3715 
Tel: 01-437 8204 
Tel: 01-437 9155 
Tel: 01-262 0387 

DAV THURSDAY! 



1003 



LiND-AiR AUDiO 



C.1W1 MULTI-TESTER 




Overload protec- 
tion. '»0,000 opv. 
AC volts 10, 50, 250, 
1,000 v. DC volts 
5-23, l'.'fi, 500, 
2o00v. D.C. Current 
0-50 uA, 0-260 mA. 
Resistance 0-60K 
0-6 Meg ohm. Deci- 
bels -20 to +22i3B. 
3 J x lin. Complete 



£4 25. P. & P. 17ip 



C.1050 MULTI-TESTER 

10,000 opv. 
RANGES: 
DC Voltage: 0-3-15- 
1 50-800-1200 Vol! 
(10,000 ohms per 
volt). 

\C Voltage: 0-6-30- 
:i00- 1200 Volt (5,000 
ohms per Volt), 

In: Current: o-lau uA, 0-300 mA. 

Resistance: 0-MK, 0-6 Meg (E x 10) 
(R X IK) 

Decibels: -20 to + 17dB. 

£5 97±. P. & P. 17±p 




SINCLAIR PROJECT 60 




• ill •••§ 



\n rill rati in aJtufiun i\e fur thr 
' athu^iaa' prepared to assemble these 
excellent modules to make a stereo 
us sem b ly . Z. 30 24 w alt Fo w er 
Amplifier £4' 47 A ®> required). 

Stereo Sixty Control /Pre-ampLLfl.er 

£9-97*. 

PZ.5 Power Supply Unit 

£4-97*. 

SISCLAIB PROJECT SO Package deal 
nrice £19.95. p. & p. 62 ^p 

Project fiO U supplied complete with 

■ r > ■- 1 ft 3 r ■ : i m 1 1 manual and templates for 
idinth mount ma,. 



C.10S2 MULTI-TESTER 

[ft RANGES: 
'" AC Voltage: 6, 30, 
120, 300, 1200 
' 15,000 Ohm/V) 
1>C Voltage: 0-6, 3, 
IS, 60, 300, 1200 
(30,000 lhm/V) 
nl: 0, 03, ii, 30, 300 mA 
Resistance: 0, 6k, 60k, 600k, 6 M ohms 
Decibels: -20 to +63dB. 

£735. P. & P. 17*p 




SM-370 
MULTI-TESTER 

20,000 opv. 

RANGES: 

DC Voltage: 0-5-25-100- 

500- 1000 V {20.000 ohmaj 

V). 

AC Voltage: 0-5-25-100- 

.'>00-1000V (-20.000 ohnw/ 

V). 

DC Current; 0-50 uA, 0-250 mA 
Resistance: RX10, RX1K (300 ohms and 
30K obtns at centre scale). 
Decibels: — 2©d_B to +16dB. 

£3-55. P. &. P. 17ip 




BATTERY ELIMINATOR 




I ' 11 ii '!'■ ": •; - 

transistor 
equipment 
to be oper- 
ated from 
AC mains. 
6/9/12V. out- 
put selector 
switch and 
2* 



£2-97±. P. & P. 17|p 




WELLER 
"EXPERT** 
SOLDERING 
GUN 

Comfortable and easy to tist\ U-fcU*.", AC, 
Instant dual heat 100/140 watt with two 
position trigger control, 

£3-37±. P. & P. 27*p 



SINCLAIR IC-10 

INTEGRATED 

CIRCUITS 

10 watt Amplifier. Size only 1x0-4 
X 0-2 in. A true hi-fi amplifier com- 
plete with manual giving details ol a 
wide range of applications and 
Instructions. Guaranteed 5 years. 

£2-97±. P. & P. 7±p 

SPECIAL TRANSFORMER FOR 
OPERATING SINCLAIR TC-10 
from A.C. mains 230/-250v. Output 
I3v at n-,1 amp. 82! p. P * P. 12! I' 




UNILEX 
AUDIO 
MODULES 

Build a stereo 
amplifier for as 
little as 

£16'75. Send :iSp fur Mullar.l 
■Do Tt Yourself Stereo" booklet 
All items In sW!< 



E.M.I. LOUDSPEAKERS 

MODEL 460 
131* x 8* ellip- 
tical wttb twin 
tweeters, 8 ohm 
impedance. 10 
watts. Brand 

Xew, guaranteed, 
Llnd-Air Price 

£3-97*. 

P. & P. 22|p 

MODEL 150 

134" X 8" ellip- 
tical, 3 and In 
ohm impedance. 
10 watts. Lind- 
Air Price 

£2 97*. 

P. & P. 22±p 




CELESTION 
LOUDSPEAKERS 

7" x 4" elliptical, 8 ohms. Jfew and 
guaraiiteedL £<-37i 

P. & P. 22±p 

CABINETS FOB ABOVE 
Teak flnisb with cloth fronts. 

£2-474 each. P. & P-22*pl 



CARTRIDGE 
BARGAINS 

A.D.C. 220X 

A.D.C. 220XE ... 



£3.961 



A.D.C. 660XE £16 



:,:>.\ 



A.D.C. 990XE £13 

Audio Teebnlca AT66-7D . . £6.12) 

Audio Technics AT68-5D . . M.1E) 

Audio Tcehnlca AT66 £6.12! 

Deeea Doram Stereo 1S.121 

Decca Denun Mono £3 .16 

Goldring Q800 £11.76 

GoldTing 800H £10,50 

Goldring Q800 E £18.50 

Goldring 0800 Super E . . £2f .00 

Goldring G860 £f .60 

ShnreMSDM £7.41 

Shure M44 7 £1' .15 

Shure M31 E «1 .00 

Shure MBS E £U,50 

Shure M75 E £21 .30 

Shore VIB II £41 .76 

Sonotone 9TAHCD £1.75 

Full range of diamond stlyll ava able 
for most current eeramki and crystal 
cartridges. All at £1 -25 each. P. ft p. 
5p. Please state cartridge make and 

t v pp n umber. 



SANSUI 
SPECIAL PURCHASE 

SATE OYER 114 
FAJtTASTIO SAHSUI BOOAl./PM 

MULTIPLEX STEREO TUNEB 
AMPLIFIER 



Solid state 17 watts music power. 
Fully tunable over Medium wari anil 
VHF/FM Stereo. Inputs for rram 
and tape etc. Host of outs tar ding 
features — details on request. 
Bee. Retail Price £89.90, 
LTND-AIR PRICE 

£75-60. P. & P. 57p 



DE-LUXE STEREO 
HEADPHONES 




WiLh raofl rubber earpiece?. 
Impedance 8-16 ohm*. Frequency 
response 23-13,000 cpn, Witn lent! 
and stereo ping. 

£2-97*. P. & P, 17*p 

STEREO HEADPHONE 
JUIfCTtOH BOX 

Enables Stereo headphones 1 3 be 
used with any amplifier, 

£1-47±, P. & P. 12±p 



HI-FI CATALOGUE 



[KJpSR JVijDIO 

mwu^ J 

I970 <& 



I DO paces lullv 
illustrated: m 1th 
* page P,A, 
-ection. All 
leading makes 
;ind acce3i.nrit-.H 
iilu* deta is of 
lludget Stereo 
iiyRteme. 

25p 

P. A P, 5p 



GARRARD HI-FI 
TURNTABLES 




20l*5 »/0 with stereo cartridge £8.87f 

3000 with Sonotone 

UTAH CD stereo cartridge £10.971 

SP25 Mk III £lE.B7i 

St65 B £16.971 

Base and cover for above 18.971 

AP76 119.50 

SL72 B £24.97 i 

SL75 B 1S8.S5 

SL95 B £89.46 

Base and cover for above . , £8.97 ■ 

401 £28 .50 

P. & P, Decks 621 p. Base 4 Cover 50p. 
Deck/Rase/Covec 871 p. 

THIS MONTH'S 

SPECIAL OFFERS! 

SP25 Mk III with base £12.871. P, * P. Top 

SP-25 Mk ITT with Sonotone 9TAHCD 

t-art ridge and ba*p 116.7S1- P. A P. 7.">p. 



LA. 20 STEREO SYSTEM 
SAVE\ 
£12 / 




Only takes a few nitnutes to set up the 
Lind-Alr LA 20 Stereo Amplifier with the 
Garrard 2025 T/C Record Changer fitted 
stereo cartridge and a pair of Llnd-Air 
General Purpose speakers and you have a 
superb stereo system at a money saving 
price. Total Eec. Price 163,471. 

Price £41-47*. C. & Ins. £1-75 



S-DeC BREADBOARD 




18/19. 25 & 53 TOTTENHAM 
COURT ROAD, LONDON W.I 
Tel: 01-580 2225/7679 
Open 9-6 Mon-Sat (Thurs until 7) 



All Mail Orders and enquiries to Dept. PW4, 
Kirk ham House, 54a Tottenham Court Road, 
London, W.l, Tel, 01-637 T GO I. 



94-96, UPPER PARLIAMENT 
STREET, NOTTINGHAM 
Tel: Nottingham 40403 (STD 0602) 
Open 9-6 Mon-Sat (Weds until 7.30) 



Solderlesa breadboard panels, for fast 
reliable component connections. 
Single DeCs. One 8-DeC with Control 
Panel, Jig and Accessories for solderless 
reumecttonB to controls, eto., with booklet 
"Projects on S-DeC" giving construction 
details for a variety of circuits. 

£100. P. & P. 17lp 

4-DeC KIT. Four S-DeCs with two Control 
Panels, Jlgn and Accessories and the booklet 
"Projects on S-DeC" all contained in a 
strong attractive plait Je ease. Ideal for the 
professional user. 

£3-95. P. & P. 22±p 

T-DeC KIT £2-50. P. &P. 17ip 
S-DeC 9TQR £ 2 -50. P. & P. 22*p 



1004 



PRACTICAL 

WIRELESS 



VOL 46 N0 12 



Issue 770 



APRIL 1971 



TOPIC OF THE MONTH 



Servicemen all 

THIS MONTH readers might feel that the issue is heavily 
weighted in favour of test instruments, for not only do 
we have a special 8-page supplement on the subject but 
two major supporting articles describe the construction of 
test instruments. Our excuse is that apart from readers 
who enjoy trying their luck at repairing the family radio set, 
many others get bitten harder by the servicing bug and 
relish the challenge of tracing faults and the satisfaction of 
a successful repair. No doubt about it, the acquisition of 
the ability to probe around inside a piece of equipment and 
come up with the right answers, works wonders for self 
esteem I 

The idea behind the supplement this month is to provide 
a broad survey of the test instrument scene, examining the 
features of the various items of equipment and outlining 
their applications. This will be followed in the May issue 
by the first of a brand new series of articles on radio and 
audio servicing conducted by those two old PW favourites 
Gordon J. King and H. W. Hellyer, voted for previous 
efforts in this field as top of the work bench pops. 

But servicing is really only one side of the coin, because 
everyone — from the absolute novice upwards — needs some 
test equipment, even if this consists solely of a cheap test 
meter, or a battery and bulb to make continuity checks! 
It is fairly safe to say, therefore, that constructors alike 
from novice to expert, experimenters as well as dabblers 
and professionals in servicing should have some knowledge 
of fault finding techniques. But in order to carry out logical 
fault finding it is necessary to have a reasonable theoretical 
grounding — somewhat of a vicious circle. The new series 
starting next month will, we hope, be helpful in providing a 
foothold for readers wanting to take a more active partjn 
servicing activities. 

W. N. STEVENS— Editor 



P.W. COVER PRICE 
Owing to the rising costs of production, it has been 
necessary to increase the cover price of Practical 
Wireless to 20p (4s. Od) with effect from the next, May, 
issue. Much as we regret this increase, it has been made 
inevitable by the hard economic facts of publishing in 
these days of spiraling prices. 

Existing subscriptions will, of course, continue to run 
out to their normal expiry date. The new subscription 
rate will be £265 per annum. 



NEWS AND COMMENT 



Leader 


1005 


News . . . News . . . News . . . 


1006 


Electro notes by S. Ginsberg 


1022 


On the Short Waves 




by Malcolm Connah and 




David Gibson, G3JDG 


1025 


Practically Wireless by Henry 


1050 


MW Column by Charles Molloy 


1058 


CONSTRUCTIONAL 





P.W, Workshop Oscilloscope, 

Part 1 by A. Lester-Rands 
"Rate your Reflexes" 

by Haivor Moorshead 
Hi-Z Voltmeter by C. R. Bradley 
Take 20, Rain Alarm 

by Julian Anderson 
Sound Effects Synthesiser, Part 2 

by F. C. Judd 
I.C. of the Month (Digital Counting 

and Display Devices) 

by L. A. J. Ireland 
"Trojan" Top Band Transceiver, 

Part 2 by Eric Dowdeswell, G4AR 1053 
A Small-C Checker by Arthur Dow 1061 
P I u g - i n T u n e r by Richard Collin s 1 065 



1008 

1012 
1016 

1029 

1044 



1051 



OTHER FEATURES 

The Committee Super-FET 
Going Back by Colin Riches and 
Arthur Dow 

SPECIAL FEATURE 



1030 



1069 






Guide to Test Instruments 
by Gordon J. King 



1033 



MAY ISSUE WILL BE PUBLISHED 
ON APRIL 8th 




news... News... news 



1971 R.S.G.B. President 




At a reception held at the Bonnington Hotel, London, on 15th January, 
F. C. Ward G2CW, Secretary of Derby and District Amateur Radio 
Society, was installed as president of the Radio Society of Great Britain. 
Over 150 guests attended the function, including J. Swinnerton G2YS, 
J. Graham G3TR, V. Desmond G5VM, W. A. Scarr G2WS, A. O. Milne 
G2MI, P. Hawker G3VA, W. Corsham G2UV, A. Forsyth G6FO, T. 
Hughes G3GVV, and L. Newnham G6NZ. Also present were represen- 
tatives of the Ministry of Posts and Telecommunications, and 20 visi- 
tors from Derby including Mr. A. G. G. Melville, president of Derby 
and District Amateur Radio Society, and his wife. 

The Mayor of Derby, Alderman Miss M. E, Grimwood-Taylor 
(whose father was a founder member of the Derby society) sent Mr. 
Ward her congratulations and best wishes. 

Mr. Ward is employed by the Post Office Engineering Department, 
and at present is in the Radio Investigation Service. He is keenly 
interested in the history of amateur radio, and mainly through his 
efforts, Derby and District Amateur Radio Society (the oldest such 
society in the country) has a comprehensive collection of documents 
and equipment from the early days of amateur radio. 

In his speech at the reception, the new president expressed the 
hope that all members of the R.S.G.B. would endeavour to enrol at 
least one new member, the aim being to double the existing member- 
ship by the end of his year of office. 

Mr. Ward's call-sign G2CW was issued to him in 1937. He is active 
on all bands from 160m down to 2m, and, he says, would be interested 
in the higher frequencies if there were more hours in the day ! 



Rank and Dolby 

Rank Wharf edale have released a small Hi-Fi cassette tape recorder. 
Based on the Dolby system, this recorder, the DC9, is a four-track 
stereo /mono machine with piano key controls. Price is £115. 

It is felt by Wharf edale that the Dolby system together with other 
improvements have enabled the company to design a player with a 
performance as good or better than that of big and expensive machines. 

1006 



#»t 



North Devon A.R.C. 

The above Club has recently been 
formed. Meetings are held the 
second and fourth Wednesday in 
every month at: Crinnis, High 
Wall, Sticklepath, Barnstable, 
North Devon. Meetings start at 
7.30 but members wishing to study 
for the RAE should be there at 
6,30. Further details may be 
obtained from H. Hughes, G4LG, 
at the above address. 



Conteslitus 

Those with "contestitus" will 
be pleased to note the following 
events for the mad month of 
March. March 6-7, ARRL DX con- 
test (phone), 13-14 BERU contest, 
20-21 ARRL contest (c.w,), 27-28 
WPX s.s.b. contest. Don't forget 
to listen on April 4 in the low 
power 80 metre contest. It should 
bring out some transistor rigs 
who would appreciate a report. 



Accessory guide 

The British Radio Corporation 
has published a leaflet illustrating 
details of the wide range of 
accessories designed for use with 
BRC audio equipment. 

There are nearly 30 different 
accessories in the range, includ- 
ing synchro-amps, pre-amps, slide 
synchronisers, mains adaptors 
for portable cassettes and radios, 
stethosets, footswitches, micro- 
phones, carrying cases and 
various connecting leads. 

Each type of accessory is illus- 
trated and a short description 
gives its applications. The pic- 
ture shows a few of the acces- 
sories included. 




News... News... News 



♦ ♦* 



Price Drop 

It certainly makes a change these 
days to hear of a reduction in 
prices, but this is exactly what 
Light Soldering Developments 
have done! Having recently re- 
located the production of their 
Litestat temperature-controlled 
soldering instruments in a new 
factory, they are now in a posi- 
tion to expand production and 
reduce costs. 

They are therefore making re- 
ductions of 20% in the list price 
of both the Litestat 50 and Lite- 
stat 70 and spares including cop- 
per bits. 

The Company are also intro- 
ducing their new catalogue. In 
preparing this, they have taken 
the opportunity to incorporate 
details of all their products in 
one booklet using the A4 format 
(for our technical printing-type 
readers). Prices are shown in £sd 
and the new-fangled decimalised 
system and metric equivalents of 
all dimensions are given. Further 
gen from: Light Soldering De- 
velopments Limited, 28 Sydenham 
Road, Croydon, CR9 2LL. 



Distribution Panel 




A new, multi-socket mains distribution panel is now included in the 
Lektrokit range. 

Designated the LKU-413, it consists of four, 3-pin, 13A shuttered 
outlet sockets, mounted side-by-side on the top of the unit, a combined 
on /off switch and magnetic circuit breaker, a red neon indicator and 
6ft. of extension cable as standard. 

Available direct from the manufacturers, the new unit is priced 
at £6.30 including purchase tax. If required, the panel can be supplied 
with 30ft. of cable (LKLM13L) at an inclusive price of SG-fflh- A.P.T. 
Electronic Industries Ltd., Chertsey Road, Byfleet, Surrey. 



Sony mini-colour TV. 

The Sony Corporation of Japan are introducing a 
"transportable colour TV set (Model KV-1320UB) 
using their Trinitron colour c.r.t. Price is £199.75 
and screen size is I3in. The Trinitron tube has only 
one electron gun against three of a conventional 
Shadowmask tube. This gun emits three simultaneous 





OPTICAL MODEL OF 

TummtoN principle 




OPTICAL. WJOELOP 
SHADOW HUK PHI NCI Pit 



Diagrammatic representation of the Trinitron principle 
compared with that of the Shadowmask system. 




Sony KV-13SOUB Trinitron colour TV. 

in-line beams which are converged and focused 
through the Trinitron electro-optical system con- 
sisting of two large diameter lenses and a pair 
of electron prisms. An aperture-grill is mounted 
behind the screen and takes the place of the 
Shadowmask used in conventional tubes. 

A description of the Trinitron tube appeared in 
the September 1970 issue of our sister magazine 
Television. 



1007 




A. LESTER-RANDS 



PW WORKSHOP 

Oscilloscope 



ON examining the circuit for the workshop 
oscilloscope, readers may wonder why valves 
have been used for the P.W. Workshop Oscil- 
loscope. First of all, a cathode ray tube requires a 
heater voltage and high h.t. potentials for which 
a suitable mains transformer is necessary. It was 
found that as the requirements for the specified c.r.t. 
could be met with a fairly inexpensive standard 
350-0-350v (plus heater windings) mains transformer, 
which would also provide potentials and heater sup : 
plies for a valve timebase and Y amplifier, there was 
little point in using transistors for a job which valves 
would do just as well and at no extra cost. 

Most low cost general purpose oscilloscopes 
presently available use valves and as far as cost is 
concerned, the P.W. Workshop Oscilloscope can be 
built for much less than a commercially made equiva- 
lent. 

CIRCUIT FUNCTION AND FACILITIES 

The P.W. Oscilloscope is intended for general 
workshop use and is suitable for all audio work and 
many r.f, applications up to frequencies of at least 
2MHz at which the main Y amplifier response is 
— 3dB but extends up to nearly 5MHz. The fastest 
timebase speed allows the resolution and display of 
several complete cycles at frequencies around 1MHz 
and the slowest speed will allow the display of several 
complete cycles at frequencies as low as 10Hz. 

The main Y amplifier has an input sensitivity of 
250mV r.m.s. for a display of 4cm peak-to-peak (sine 
wave) and a nominal frequency response of 10Hz to 
2MHz. The Y preamplifier has an input sensitivity of 
lOmV for a display of 4cm peak-to-peak (sine-wave) 
and a frequency response of 10Hz to 50kHz ± IdB. 
This additional stage to the Y amplifier chain is to 
provide adequate signal display from low level signal 
sources. The gain of the Y amplifier is continuously 
variable, regardless of which input is used, and each 
of the inputs have relatively large overload margins. 
The gain of the Y amplifier has been adjusted, in 
the relationship to the c.r.t. sensitivity, so that the 
final amplifier stage reaches clipping point after full 
Y plate deflection. 

The timebase is a Miller-transitron circuit with 
its own sync amplifier that can be switched for inter- 
nal or external signals. Each timebase range is con- 
tinuously variable and each overlaps. The timebase 
can be switched off and the sync selector switch used 
to provide a small 50Hz sweep (internal signal source) 
or select a separate X plate amplifier with its own 

1008 




Specification 



Frequency Responses 

Y amplifier .. 

Y preamplifier 
X amplifier 
Timebase frequency • . 



10Hz to 2MHz 
10Hz to 50kHz 
10Hz to 50kHz 
10Hz to 24kHz 



Input Sensitivities 

Y amplifier . . . . 4cm deflection for 250m V 

Y preamplifier . . .. 4cm deflection for 10m V 
X amplifier .. .. 4cm deflection for 1-5V 
(Deflection peuk-to-peak, volts In r.m.s.) 



Controls 

1. Y amp. gain 

2. Timebase Function 

3. Y preamp., in/out 

4. Timebase sweep 

5. Timebase flue sweep 

Timebase Ranges 

1. 10-50HZ 

2. 3O-270HZ 

3. 9O-e00Hz 



6. Timebase amplitude 

7. Brilliance 

8. Focus 

9. Y shift 
10. X shift 



4. 500-4,50QH* 

5. 2,700-24,0O0Hz 

6. Off. 



Valve Lineup 

CRT. CV1526 (3EG1), 3-Off EFSO's, ECC81, ECC83, 
ECF80. 









ECU 




ic components list 



Case as used for prototype 

Corttil type Q 13 x 9 x 7in. West Hyde Develop- 
ments Limited 
Cathode Ray Tube 

Type CV1526 (3EG1) Henry's Radio or 

2£in, screen. Green trace RST Valve Company 
12-pin B12B Base P.C. Radio Limited 

(Price should be around £3-25) 

CRT Base 

12-pin B12B (suppliers as above) 

Mains Transformer T1 

230V pri-Sec. 350-0-350V SOmA 

Heaters 6-3V and 4V Type MT2 Home Radio 

(Catalogue No. TM2) 

Rectifiers (SR1, 2, 3 and 4} 

SRI, 2, 3 and 4 Type 1N2374 Silicon Henry's Radio 

Limited 
Valveholders 

B9A 9-ptn (6 of!) 

Valves 

VI. V3, VS EF80 Mullard 

V2A-B ECCS1 Mullard 

V4A-B ECC83 Mullard 

V6A-B ECF80 Mullard 



Diodes 




D1, D2 


OA81 Mullard 


Switches 




S1A-B 


2-pole 4-way 


S2 


Single pole 2-way 


S3A-B 


2-pole 6-way 


S4 


Mains on/off toggle type 



Potentiometers 

VR1 1Q0kn lin. VR8 IGOkfi lin. 

VR2 25k£l lin. VR9 500kH lin. 

VR3 2Mft lin. VR10 10kQ lin. 

VR4/5 \ohao (Dual Potentiometers) Home Radio 
VR6/VR7 j"™" 

Resistors |W 10% 



(Catalogue No. VR78/2M) 



1-5MQ 
470kfi 

ikfl 

47kQ 
47kQ 
1Mfi 
100kn 
27kQ 
10kfi 
R10 15kfi 
R11 100kn 
R12 tokO 
R13 4-7kfi 



R1 
R2 
R3 
R4 
R5 
R6 
R7 
R8 
R9 



R14 150kQ 
R15 1MH 
R16 1-2MQ 
R17 100kQ 
R18 10MD 
R19 2-2kfl 
R20 2-7kO 
R21 2-2Mfi 
R22 2-2MD 
R23 2-2Mfi 
R24 2-2MU 
R25 47k£> 
R26 10kfi 
All resistors 



R27 47kO 
R28 100kO 
R29 1MQ 
R30 2-2MJ3 
R31 22MC1 
R32 1MQ 
R33 56kQ 
R34 22kQ 
R35 68kO 
R36 1-5Mfl 
R37 1MQ 
R38 330Q 
R39 10kfi 
10% iWatt 



R40 270D 
R41 5-6kO 
R42 1M12 
R43 270O 
R44 5-6kD 
R45 10MO 
R46 22kD 
R47 22kO 
R49 2-7kO 
R50 150kO 
R51 47kD 
R52 1kO 
R53 10kQ 



Resistors (Special) 
R54 5kft Swatt 
R48 lOkft 2watt 



Capacitors (special) 
C40 1/iF paper type — 500/ 600V working 



Home 
Radio 



Capacitors 



C1 

C2 

C3 

C4 

C5 

C6 

C7 

C8 

C9 

C10 

C11 

C12 

C13 

CI 4 



0-1//F 
022/iF 
8<wF 350 V 
2200pF 
WfiF 350 V 
0-01/iF 
0-1/*F 
0-02;jF 
6800pF 
1200pF S.M. C24 
250pF £25 

250pF S.M. C26 
1200pF C27 

F 028 



C16 
016 
C17 
C18 

C19 
O20 
021 
022 

023 



Q-02^F C29 
0*1/*F C30 

0-1/iF C31 

33pF S.M. C32 
005/<F C33 
33pF S.M. C34 
0-25,«F C35 
0-25/<F C36 
16,uF 450V C37 
16/xF 350 V C38 
0-V<F C39 

25/iF 50V C4t 
0-1juF C42 

500pF S.M. 



500pF S.M. 
005//F 
0-22/^F 
0-22/xf 
16juF 450V 
16/jF 450V 
16/jF 450V 
16/iF 450V 
O'ImF 
I^F 450V 
1^F 450V 
8/i F 450V 
S«F 450V 



Note: C33/C34— maj be dual type capacitors 
C35/C36 — may be dual type capacitors 
All other electrolytics must be singles and all 
capacitors 350V working min. 
S.M. — Silvered Mica 



Miscellaneous items 

; Terminals 2 red,, a black (X and Y inputs) insulated 
type 

Sockets (Insulated) 2 for sync and cal. voltage 
Socket Recessed co-axial type 
Pointer knobs 1D off 
Mains panel neon indicator 230V 
Insulated spindle couplers (focus and brilliance 
controls) 2 ofi 

2-18 way and 4-10 way miniature tagboards Hin. 

wide 

Aluminium 18 swg for screen etc. 

Aluminium angle § x fin. 

Paxoiin or perspe< £in. thick for brilliance and focus 

controls 
Sundry capacitor clips and chassis tag strips 
1 6-way standard tagboard 2in. wide 



(pre-set) gain control. This latter facility is extremely 
useful for Lissajous pattern work over a wide fre- 
quency range and with low signal levels. The X ampli- 
fier sensitivity is 1 ■ 5V rms for a 4cm peak-to-peak 
(sine-wave) display and the frequency response is 
10Hz to 50kHz ±ldB. 

CONTROLS 

The timebase controls include a selector for the 
five timebase ranges plus a timebase 'off' position, 
a timebase fine frequency control and a timebase 
amplitude control. The 'sync* switch selects either 
internal or external synchronizing signals, a 50Hz X 
sweep of about 1-Scm, or the X plate amplifier. Bril- 
liance and focus controls are provided, of course, 

1010 



and there are controls for X and Y shift with suffi- 
cient shift potential to move the trace vertically or 
horizontally to beyond the edge of the c.r.t. screen. 
The Y amplifier gain control is common to both Y 
inputs and is a front panel control but the X ampli- 
fier gain control is a pre-set mounted at the side. It 
can be easily adjusted with a screwdriver. 

THE CATHODE RAY TUBE 

Cathode ray tubes of currently available manufac- 
ture and type are quite expensive and are also diffi- 
cult to buy because the demand is so low that few 
component dealers will keep them in stock. The tube 
chosen for the workshop oscilloscope is a type CV1526 
(3EG1) which is readily available at low cost (see 
components list) and has a 2 1 2in. diameter screen. 



It operates with a final anode potential of approxi- 
mately 1,000V and displays a green trace. It should 
be emphasised that the workshop oscilloscope has 
been virtually designed around this c.r.t and that the 
use of any other type is not recommended. 

THE CIRCUIT 

The full circuit for the oscilloscope is shown in 
Fig. 1. E.H.T. for the tube final anode is derived 
from a voltage doubler arrangement (SR1-SR2) 
operated from one half of the secondary of Tl, the 
600V or so d,c. obtained from this being connected 
in series with the nominal 350V supply (SR3-SR4) 
to obtain the required total 1,000V or so. The 350V 
supply from SR3-SR4 provides the working potentials 
for the timebase, the X and Y amplifiers and the 
shift controls. The timebase generator, V3, is a con- 
ventional Miller-transitron arrangement and is fol- 
lowed by a paraphase amplifier, V2B, to provide 
balanced sweep voltages for the X plates. The time- 
base frequency ranges, each of which overlaps the 
other, are selected by S3A and B and the total fre- 
quency range is approximately 10 to 24,000Hz. Fine 
timebase frequency control is obtained by VR3 and 
amplitude by VR2. Synchronizing signals for the 
timebase can be supplied from either the Y amplifier 
at the cathode of V4B, or from an external source 
via the 'sync' switch SI A and B. This also selects 
the internal 50Hz X sweep voltage from the 6-3V 
heater supply or switches in the X plate amplifier VI. 

The main Y amplifier is preceded by a cathode 
follower (V4B) which provides a high impedance 
input and low impedance output via the gain control 
VRI0. The Y amplifier itself consists of V5 and V6A 
the output of which is terminated by the phase sput- 
ter V6B. This delivers symmetrical paraphased sig- 
nals to the Y plates via the isolating capacitors C31 
and C32. For low level signals the additional Y ampli- 
fier stage (V4A) is provided and this has an input 
sensitivity of lOmV for 4cm peak-to-peak deflection. 

The c.r.t. operates at a potential of approximately 
1,000V between cathode and the final anode. The 
potential dividing chain R27, VR8, VR9 and R29 
provides the brilliance and focus control voltages. 
The grid of the c.r.t. is returned to the cathode via 
R26 but is also connected via C17 to obtain a nega- 
tive going pulse for trace flyback suppression. 

The X and Y plates are both connected to the shift 
potential networks VR4, VR5, VR6 and VR7, etc. 
via high value series resistors (R21, R22, R23, R24) 
so that no loading is imposed on either the X or Y 
plates or their respective amplifier outputs. The shift 
potential developed across VR4, VR5, VR6 and VR7 
at the points marked 4- a and +b is approximately 
200V and is sufficient to move the trace vertically 
or horizontally completely off the tube screen. A 
lOOmV 50Hz calibration signal is derived from the 
6-3V heater supply via the potential divider R49/R50. 

PERFORMANCE 

The workshop oscilloscope will cater for all 
normal audio tests including square-wave testing, 
frequency measurement by the Lissajous pattern 
method over a wide range of frequencies and signal 
levels and has many general "electronics" radio and 
video frequency applications. The Table gives details 
of the performance obtained with the prototype and 
which should be easily obtainable from the circuit 
shown in Fig. I, providing the specified c.r.t. and 
other components are used. 



liance is 



X SWEEP 

With the tube E.H.T. at 1,000V the brilli 

sufficient for photography and the trace focus is sharp. 
It is worth noting that no spurious spot deflection 
due to mains transformer field was discernible and 
providing the transformer specified is used and posi- 
tioned below and to the rear of the c.r.t. as will be 
shown later, it should be quite unnecessary to pro- 
vide mumetal shielding. With the timebase range 
control switched to 'off' and with the Y amplifier 
gain control at zero, the spot should appear com- 
pletely round and sharp and not more than 1mm in 
diameter at normal brilliance. Note also that with 
the X and Y shift controls at exactly half way travel 
the spot should be at the centre of the screen. 

CONSTRUCT/ON 

The prototype was constructed exactly in accord- 
ance with the circuit given in Fig. 1 and as shown 
in the photographs, in a Contil case type Q (see 
components list). This has overall dimension of 13 X 




The insulated supporting bracket and insulated spindles for 
the focus and brilliance controls, 

9X7in and is supplied with an internal chassis on 
which the c.r.t., the power supply and amplifier com- 
ponents and valves are mounted. A home constructed 
case of similar dimensions could of course be used. 
Construction also calls for an internal screen which 
supports the tagboards for the amplifier and time- 
base components, supporting brackets for the c.r.t. 
and the X amplifier gain control and a bracket of 
insulating material (paxolin or perspex) for mounting 
the brilliance and focus controls. Full details for 
construction and layout will be given in Part 2. 



TO BE CONTINUED 



1011 







THE project described here has several uses. It 
will do as the title says : "Rate Your Reflexes" 
— but it also enables you to test your reactions 
against those of other people. It can incorporate 
other tests including manual dexterity and it is a 
very effective "Drunkometer" which will prove to 
yourself — or to other people — just how much alcohol 
affects your reactions. There aren't many ways of 
arguing with the man who says "I'm perfectly safe 
on the road after eight pints, etc." but this device 
will show him just how much slower his reactions 
are even after only a couple of pints. The results 
will be there for him to see for himself. 

It is often true that the simplest games and tests 
are the most fun and that certainly applies to the 
reaction tester described here. At parties it has 
proved a real winner. Rather like the fortune teller 
who is never short of customers because people 
always want to know something about themselves 
that only someone else can tell them, the reaction 
tester will tell people how their reactions or reflexes 
compare to the average. Unlike the fortune teller, 
however, this device is scientifically accurate to 
quite a high degree — you yourself determine the 
readings and they cannot be disputed. Once people 
have got the hang of it the reaction tester fascinates 
them. 

The reaction tester has proved so popular that 
those who have tried it have devised all sorts of 
games and tests. Some of these are mentioned at 
the end of the article but no doubt many will occur 
to you. 

Operation 

There are two distinct ways of using the circuit. 
Firstly there is the competitive side — at a signal 



HALVOR MOORSHEAD 

two "players" try to throw a switch as fast as pos- 
sible, the one who is fastest is shown to be the 
winner by a second bulb lighting up above his 
switch. Even though the loser is a thousandth of 
a second behind the winner his bulb will fail to light 
and will not do so until the winner's switch is reset. 

The competitive side can be built separately and 
will provide plenty of fun for very much less cost, 
but it does have limitations — it will only tell you 
who is the fastest of two players but no indication 
of the differences in their speeds and you cannot 
use it without another player. 

The timer part of the circuit is additional and 
works as follows. As soon as the start signal bulb 
lights up, the needle of a meter starts to rise — and 
rise quickly — taking about a second to traverse the 
scale. As soon as the switches are thrown the needle 
stops and stays in the same position so that a read- 
ing can be taken of the time lapse between the "start 
signal" and the winner throwing the switch. It will 
of course only give the reading for the winner. 

A considerable amount of thought was given to 
including a "cheat" device, that is one which would 
light up a bulb or sound a hooter if either switch 
was thrown prematurely but so much trouble was 
experienced with this that it was decided to leave 
it to the end. To the author's delight it was dis- 
covered that a "cheat" circuit is actually built into 
the existing circuitry and this will be explained 
later. 

Although it may be rather pretentious, you could 
call the finished project a simple computer for it 
includes computer type circuits and this claim, made 
to non-electronic friends, should impress them! 

The Circuit 

There are three distinct sections to the circuit 
and these will be explained separately. They are 
the "start signal", the "winner" circuit and the 
"time indicator." 

The "start" signal circuit should ideally be operated 
independently of either competitor and also ideally 
one would use some form of random circuit. How- 
ever random circuits are very complex and it would 
be impractical to use one here. 

The next best thing — and perfectly satisfactory in 



1012 




SW4 




'<1 T 



>^ 



Fig. 1 : The complete circuit of the 
Reaction Tester, Tr 1 and Tr 2 form 
the delay circuit which relies upon 
the charging of CI. Tr3 and TR4 
are coupled as a Darlington pair to 
form the high input impedance 
timing circuit while TrS and TrS 
are part of the "winner" indicator 
circuit. 



use — is to use a time delay circuit in which the delay 
is of sufficient length so that it is impossible to 
remember or estimate exactly when the "start" 
signal will trigger. 

Trl and Tr2, together with the associated com- 
ponents, act as a time delay circuit, the delay vary- 
ing between instant and about 12 seconds. A longer 
delay was originally included but it was found that 
delays of much more than about ten seconds served 
no real purpose and tests became boring. A period 
of 12 seconds when you are waiting for something 
to happen is a very long time indeed. 

The "start" signal circuit makes use of a Schmitt 
Trigger — that is a circuit which can only be in two 
states, on or off, and the switching action is very 
fast indeed. 

Referring to Fig. 1, when SW1 is thrown to "on", 
CI begins to charge through VR1. To begin with the 
potential across it is small — as it is charging — and 
therefore the base of Trl, which is coupled to the 
junction of CI and VR1, is at nearly supply poten- 
tial and is switched fully on. This means that it is 
passing considerable current and the potential be- 
tween the collector and emitter is very small. The 
base of Tr2 is coupled to the collector of Trl via a 
resistor R2 and the emitter joins directly to the 
emitter of Trl. 

When Trl is "on" the potential across it is so 
small that Tr2 will not have nearly enough potential 
between the base and emitter to be in a conducting 
state and will be completely "off" and the bulb LP1 
will be off. 

However, as CI charges the potential across it 
increases and the base of Trl is moved slowly to- 
wards chassis potential until a point is reached when 
Trl approaches cut-off; this means that the potential 
across it rises and this in turn means that Tr2 starts 
to turn on. There is a regenerative action because 
of R3 and the switching action, once it starts, is very 
rapid. When Tr2 is on, current is allowed to flow 
through it and the bulb LP1 lights up. 

The time delay will depend on the setting of VR1 
and as mentioned this can be adjusted for any set- 
ting up to 12 seconds. 

The values of Rl 7 R2 and R3 are not over-critical 
for the operation of the bulb but their choice does 
affect the operation of the timer circuit which com- 
prises Tr3 and Tr4 with their associated components. 

When the "start" circuit is triggered the potential 



ic components list 



Resistors 

R1 15kfi 
R2 3-9k£l 
R3 39Q 
R4 330Q 



R5 33Gn 

R6 120kfi 

R7 4-7kQ 

R8 330Q 



All resistors £W, 10% 

VR1 1Mfl linear track potentiometer. 

Capacitors 

C1 iGOixF 12V or higher. 

C2 16^F— 10V, Mul lard— see text 



Semiconductors 

Tr1 2N2926G 
Tr2 2N2926G 
Tr3 2N2926G 
Tr4 2N2926G 



Tr5 BFY51 
Tr6 BFY51 
D1 1N914 



Switches 

SW1 2- way, 1-pofe toggle 
SW2 2-way, 2-pole toggle 
SW3 2-way, 2-pole toggle 
SW4 On/off slide switch 



Miscellaneous 

Meter 

Case 

LP1, 2 and 3 

Butbholders 

Battery 

Component Board 



100fiA, 3iin face— see text 

6V, 40mA MES bulbs 

3 MES types 

PP9, 9V. 

0-15in matrix plain Veroboard 



at the junction of Rl and R2 rises and capacitor C2 
begins to charge through R6 and Dl and this in 
turn starts to bias on the high impedance circuit 
(the Darlington Pair) comprising Tr3 and Tr4 in 
which the current increases with the rise in voltage 
at the base of Tr3. Even before the "start" circuit 
has triggered there is of course a small potential 
at junction Rl and R2 and the capacitor will be 
charged but it is not enough to bias the Darlington 
pair into conduction. 

As soon as either of the competitive switches are 
thrown the charging line is broken and C2 is no 
longer being charged. 

As the input impedance of the meter circuit is 
very high — in the order of lOOMft — so little current 
will be drawn from the capacitor that it can be 



1013 



ignored and so the meter continues to register a 
nearly true reading of the charge on the capacitor. 
This is of course proportional to the time which has 
elapsed between the light coming on and either of 
the competitive switches thrown. 

The needle will rise very fast but, once stopped, 
will stay there. In fact the needle will fall very 
slowly due to the leakage of C2 and to a far lesser 
degree due to the current taken for Tr3, but the 
fall on the prototype was only about one division 
on the meter in ten seconds, a division being one 
fiftieth of full scale deflection. 

The quality of the component used for C2 is 
important. One of the Mullard "Blue" range was 
used as these appeared to be very much better than 
imported types at holding the charge. Some Japanese 
components hardly held any charge at all, the 




Fig. 2 : The drilling of the face plate on the prototype. As can be seen 
from the heading photograph, this is angled. 



leakage was so high. It is certainly worthwhile choos- 
ing a good component for C2 by experiment. 

R6 is included to set the rate of charge. A small 
slide switch and R8 are included to shunt the meter 
to give two scales of reading. 

In the prototype the unshunted meter takes about 
a second to reach full scale deflection, the 330H 
shunt reduces the rise rates to 20% of the original. 
On the "slow" setting readings above 7 are far from 
linear but this does not really matter. 

The slow rate is only needed for certain experi- 
ments since all the simple tests can be completed 
in under a second by most people. 

The "winner" indicator circuit comprises Tr5 and 
Tr6 with associated components. Let us assume that 
the person with the most rapid reactions is on SW2. 
When this is thrown the emitter of Tr5 is connected 
to chassis and since the base circuit is biased via 
R5 and LP3, as soon as the circuit is completed by 
SW2 the transistor conducts and LP2 lights up. 
When the other person makes his switch, the emit- 
ter of Tr6 is connected to chassis but as Tr5 is in 
conduction and fully switched on the voltage across 
Tr5 is so small that there is not enough to bias the 
transistor on. It therefore remains off whatever the 
position of SW3. So it comes down to whoever com- 

1014 



pletes the indicator circuit first messes it up for the 
other. 

Since the circuit has already been broken between 
the Schmitt Trigger and the timing indicator, the 
additional break contributed by SW3b doesn't affect 
the operation and the timing indicator registers the 
winners time only. 

Cheat Circuit 

From the circuil it will be seen that LP 2 and LP3 
can be switched an regardless of whether LP1 is 
alight or not. However if this is done one of the 
bulbs LP 2 or LP 3 will light and will draw a fair 
amount of current and this is not only taken from 
the battery but also from the charging timing capaci- 
tor CI to a small degree. This has the effect of trig- 
gering the Schmbt circuit and LP1 will light. But 
since the line connecting the junction of Rl and 
R2 to R6 has been broken, the timing circuit will 
show no reading. 

It could be claimed that this would given the same 
reading as for an instant reaction and this is true 
but the fastest reactions possible (I have it on good 
authority) are in the order of l/10th of a second. 
If you believe that they are faster just try it. 
Not only does the cheat circuit work but it also 
shows who has cheated because of course their light 
is on! 



Reset 

Once a test h&s been completed it is necessary 
to discharge both capacitors CI and C2 and this is 
done by switching off for about a second. SW1 is 
arranged so that it directly shorts out CI while C2 
will discharge through the base emitter circuits of 
Tr3 and Tr4. 

C2, unlike CI, does not discharge instantly — it 
takes about half a second. If SW1 is thrown off and 
on again too quickly a small reading will still be 
shown on the meter. 

Construction 

There is available a very suitable case which 
might have been built for this very project; this is 
one of the "U" range marketed by H. L. Smith & 
Co. Ltd., of 287/11 Edgware Road, London W.2. The 
case, sized 9 1 4>C7 1 2X3 1 2in., is silver hammered 
finished and costs £1 ■ 20 plus postage and packing. 

The meter is one of the Henelec or S.E.W. types 
with a S^in. face and a large hole has to be cut in 
the sloping panel to hold it. 

These meters are supplied in a cardboard box 
with a piece of card that acts as a perfect template 
for marking the size of the hole and the positioning 
of the mounting screws. A series of holes are drilled 
just inside the area marked out to remove the main 
aluminium and a file removes the rest. 

SW2 and SW3 are mounted at the bottom left 
and bottom right respectively of the sloping panel; 
these can be marked "A" and "B" and the asso- 
ciated light mounted above them. 

The start bulb is sited on the top "flat" with the 
Off -Reset/On switch and VR1 the delay potentio- 
meter. 

The two terminal contacts on the back of the 
meter provide a very suitable mounting for the 
component board, and two holes should be drilled in 
this to enable it to be screwed on. 






Holes lor 

erminals" 



/^^Y*rrieter termtnals^/^^v 



Trl 



Tr3 Tr6 






3 



Battery — ve 

f/ff. 3: The component layout on plain Veroboard. Note that Tr3 and 
Tr4 should read Tr5 and TrG and vice versa. 




Component board 
letters refer to 
connections on 
board 




J SW3 




Compare this photograph with Fig. 4. 



C/oseup view of the component board. The meter terminals are visible 
at the top. 



The component board is made from 0*15in matrix 
plain Veroboard and should be wired as shown in 
Fig. 3. 

The wiring is shown in Fig. 4, the letters corre- 
sponding to the similar letter on the component 
board. 

Using the Reaction Tester 

It may be found on careful inspection that there 
is a very short delay between the bulb lighting and 
the needle starting to move. If this is so high that 
the fastest genuine reactions can be accomplished 
in the delay, the values of Rl and R2 should be 
experimented with. The delay is due to the voltage 
at the base of Tr3 having to reach a certain level 
before it begins to conduct. 

The first tests can be done by yourself. With SWI 
thrown to "on", switch either SW2 or SW3 as soon 
as the light comes on indicating "start". By the time 
you have thrown the switch a reading should have 
registered on the meter. 

Try part- thro wing the switch at the next test — 
that is, hold either SW2 or SW3 with such a pres- 
sure that the tumbler is just about to throw. This 
will remove as much of the mechanical delay (if 
one can call it that) as possible so that the time 
registered is only that of your reflexes. It will prob- 
ably be found that this makes little difference. Then 



try having the hand that you are going to switch 
with flat on the table and only move it when the 
light comes on and note that reading. 

One interesting point has been noticed on the 
prototype. If the unit has been off for a period of 
much over 20 minutes, the first reading will be 
much slower than subsequent ones. This is prob- 
ably due to the electrolytics reforming. For this 
reason make sure that the first reading of a series 
is ignored. 

If you leave the delay at one setting and try a 
series of tests you will find that both competitors 
get better as, even if the time delay is at maximum, 
they begin to estimate the starting signal and get 
ready for it. 

Try to take a series of twenty readings, take the 
average and have a pint of beer. After ten minutes 
or so your reactions may show a slight improvement 
but after a second pint and a further series of tests 
the reactions will show a marked decline. During 
these original tests one player was so fascinated 
that he continued to take readings till he had drunk 
eight pints — at which point he was unable to find 
the switch! 

Averages must of course be used, as a single 
reading may be a fluke, either one way or the other. 

A little ingenuity will enable you to make all 
kinds of tests and will provide hours of fun. ■ 



1015 




h 



LI 



fc— aw . wn i— il l 






VOLTMETER 




CR.BRADLEYB.Sc. 




THE improved noise performance, and only 
slightly diminished gain, provided by modern 
silicon planar transistors working at low 
collector current have encouraged the use of ever 
decreasing currents in small-signal circuits. The 
correctness of voltage measurements made using a 
conventional moving-coil multimeter therefore 
becomes increasingly doubtful, since the voltage 
conditions in the circuit may be seriously upset by 
the current 'stolen' by the meter. An example is 
illustrated in Fig. I where a voltmeter with a 50/xA 
movement, which is about the highest sensitivity 
compatible with reasonable ruggedness and price, 
reads 50% low at the base of a typical transistor 
amplifier. 

The only way to measure voltages with confidence 
is to use a voltmeter of much higher internal 
impedence than the point in the circuit tested. 
Excellent designs for high impedance voltmeters 
frequently appear and generally consist of a highly 
stable operational amplifier driving a moderately 
sensitive meter movement. However one must expect 
to invest several pounds in building such an instru- 
ment, or many more pounds to buy the cheapest 
commercial article. The author's aim was to design 
a high impedence voltmeter of adequate versatility 
for all likely experimental needs, which could be 
built for the absolute minimum cost. By careful 
shopping for components, the total cost of the proto- 
type came to £4*25, which compares well with the 
cost of a moving coil multimeter. The latter, with its 
a.c. voltage, d.c. current and resistance ranges, 

1016 



This article was 'he winner of the Project Autumn 
Silver Trophy Competition held last year. The judges 
considered it the best entry for several reasons includ- 
ing clear description and ingenuity. Although the 
likely popularity was not a major consideration in the 
judging, we believe that this project will be found to 
be very useful to the electronic experimenter. 



RANGES (D.C. VOLTS) 
0-0- 5-1 -5-1 0-5(1-1 00-500-1 000 

USEFUL MEASUREMENT RANGE 
005-1000V. All readings above 0- 25 V in upper half 
of meter scale 

CONTROLS 
Range; Switch: 1-1 0-1 00-1 OOOV d.c. 
Function switch: Off-Battery Test-Short Circuit 
Input-Measure 

Pushbutton to divide range by 2 
Internal preset for meter calibration ; 
Two internal presets for meter zerO setting with 
terminals open and short circuited respectively. 

FEATURES 
Both forward and reverse overload protection for 
mete^rnOvement Long battery life ■ 

INPUT IMPEDANCE 
Range Impedance 

0-1 V >7MH 

0-10V:: >3M£i 

0-1 00 V >5MH 

0-1000V >5MQ 



remains the essential first purchase for the experi- 
menter. 

The specification of the high impedence voltmenter 
is shown in the table. 




Fig. 1. 



DESIGN 

The very simplest circuit which has a high input 
impedence and can drive a meter is the emitter 
follower shown in Fig. 2. Here the voltage gain from 
base to emitter is unity. This is because if the base 



Fig. 2. 




voltage is increased, base-emitter current and there- 
fore collector current both increase, and the voltage 
drop across the emitter load rises until emitter and 
base voltages are similar. The 50/*A meter in Fig. 2 
has a 200kfl series resistor so we should get full scale 
deflection for 10V at the input terminals. The input 
impedance of the circuit is transistor gain X200kft 
or typically 100X200kft=20Mft. This suggests the 
circuit would form an ideal basis for a high 
impedance voltmeter. In practice two complicating 
factors arise, which are handled in the final circuit. 

The first problem is that if any current at all flows 
from base to emitter, there is a voltage drop of about 
0-7V across the junction. Thus the simple circuit 
would be useless for measuring a voltage around 
0-5V, say. The second problem is that even with 
zero base-emitter current, the transistor passes a 



► VR2 
Short- 
circuit 
zero 



>lnputO 




HT+ 



M 
50pA 



20k + /^N 
•7k< U—tVtWd .—-I *A [d 



|U£ 



Fig. S. 

certain collector-emitter leakage current. Even with 
a silicon transistor, this leakage might be 5/*A or 
more and this would show on the meter. In addition, 
these two values of 0-7V and 5/tA vary with 
temperature. 

The arrangement chosen to deal with this situation 
is shown in Fig, 3. Here the meter movement, with 
appropriate series resistor for the voltage range 
required, is connected between the transistor emitter 
and a constant supply of 8V provided by R and the 
zener diode D. Current is fed to the base by VR1 
which is set up for zero meter deflection. This occurs 
when the emitter voltage equals the zener voltage. 
The transistor is then passing a collector-emitter 
current of 8V ■*■ 2-7kfl = 3mA which leaves its 
leakage current far behind. As the base current is 
tiny (i.e: 3mA ■*■ transistor gain) a very large lOMfl 
resistor can be put in series with VR1 slider to 
preserve the high input impedance of the emitter 
follower. 

The positive input terminal is now at 8 + 0-7V, 
This voltage is also set at the negative input terminal 
by VR2, done by shorting the terminals together and 



setting VR2 for zero meter deflection. Now ready for 
measurements as low as 0-05V on the IV f.s.d. range 
shown, the arrangement is simple and cheap, and the 
only drawback compared with a more sophisticated 
balance operational amplifier is a more frequent 
need to readjust the zero controls with changes in 
temperature. 

FULL CIRCUIT 

The full circuit of the instrument is shown in Fig. 4 
and has been developed from that in Fig. 3 as 
follows. The single transistor is replaced by two 
transistors connected as a Darlington pair, which 
behaves like a single 'super' transistor whose gain is 
the product of the gains of the two separate trans- 
istors. Since the 2N2926 (green) has a specified gain 
(beta) of 235 to 470, the pair has a very high gain 
indeed. The emitter-base junction of another cheap 
silicon transistor is connected in reverse to serve as 
the zener diode in Fig, 3; this is cheaper than using 
the real thing and just as efficient. A batch of a 
dozen of this transistor all gave zener voltages in the 
range 6*5 to 9V which is acceptable for this use. 
The zero controls are combined with the zener diode 
to save one resistor (R in Fig. 3); this arrangement 
also allows finer adjustment of the two controls. 

The total series resistance of VR1, R9 and the 
5<V A meter M is arranged to be lOkil; the meter 
therefore gives full scale deflection for (50/»A X 
10W1) = 0-5V across this chain. The potentiometer 
VR1 is included so that the circuit can be set up for 
a meter movement of any likely internal resistance, 



-K components list 



R6 


10MH 5% *W 


R7 


2*7kH 5% -iW 


R8 


iokn 1 % i w 


R9 


4-7kf} 5% 4W 


R10 


2-7kfi 5% £W 



Resistors 

R1 3-3Mfi 2% *W 
R2 TWO 10Mft 2% *W 
R3 TWO 10kO 2% *W 
R4 TWO KMkQ 2% iW 
R5 390kQ 2% iW 



VR1, 2, 3 4-7kfl (or 5kQ) miniature skeleton preset 

potentiometers 

All the above available from Electrovalue, 28 St. 
Judes Rd., Englefield Green, Egham, Surrey 

Switches 

St 2- pole (or 3-pole) 4-way rotary 

52 3-pote 4-way rotary 

53 Push-to-close 

Semiconductors 

Trl, 2 2N2926 (Green) 

Tr3 2N2926 (Orange) 

D1, D3 Any silicon diode e.g. 1N914 

D2 Any germanium diode e.g. OA70 

M eter 
50/jA f.s.d., 1-5in, square approx. 
Eagle MR-2P or SEW MR.38P (latter from Barnet 
Factors Ltd., 147 Church St, London, W.2) 

Miscellaneous 

Veroboard 0-1 Sin. matrix, 1j (across tracks) x 3^in. 

Insulated terminals, red and black 

2 PP3 batteries and battery clips 

4 8BA bolts, nuts, etc. 

Scrap piece of polystyrene or foam rubber (see text) 

2 pointer knobs 

Polythene box {see text) 

Letraset for labelling 



1017 




o- 



U T fl 



Measure 



R2 

5M 
(2xlOM2 /o} 



Short, 



Ktest o . j 
Off' 



,S2o 



Sia&b ganged 
S2a,b&c ganged 




Short 4 



Measure 



* O O— 1 M 

'■' Calibrate .;;;. 50>JA ; , 

a R8 l VRf R9 ' +/C\ " 

« •— WV *-* WV H M ' CV> f t 

10k f/ 4«7k 4-7k V_V 



7>4'7k 



Short- "< 4-7k 
circuit 
Zero 



0-5Vf.s.d.-*r 



D3 

-Mr 

Silicon 



©ermanium 



IVf.s.d- 



„S2c 

n 



R10 
2*7k 



D1 

N 

Silicon 



Tr3 

2N2S26 
{Orange) 



B1 

PP3 

9V 



I 



B2 ; 

PP3 [ 

9V ' 



Fig. 4 : The complete circuit of the high impedance voltmeter. Although seemingly complex, mos' of the circuitry is simply a refinement of that 

shown in Fig. 3, See the text for an explanation of the operation. 



&. 




fft¥H7n 



To S3* : K * », f ( * 




Fig. S: The Veroboard layout of the components and the other coinections. 



1018 




introduc 




In rigid plastic "tool box" containing Model 
CN - 15 watts - 240 volts miniature iron 
fitted ye" bit. Spare bits jy" and 32". Reel 
of resin-cored solder, heat sink, cleaning 
pad, stand and booklet "How to Solder" 



E1-70 (34/-) 



Fitted with nickel plated j§-" bit and 
packed in handy transparent box. 



Mode) G - 18 watts. Fitted gf 
bit. Spare bits |", ts"" and 
£" available. For 240 or 220 
volts. £0-87(17/5). 



Model F - 40 watts. F itted ^" 
bit. Spare bits ife", 3", ^" 
5" available. For 240, 220, 1 10, 
20 volts. From £2-35 (47/-K 



Model E - 20 watts. 

Fitted \" bit Spare bits 

32 . 35" and -J^" available. 

For 240, 220 or 110 

volts. From £1-80 (36/-). 

Model ES - 25 watts. 

Fitted r" bit. Spare bits 
3 3 , 1 

32 , -fe and 4 available. 

For 240, 220 or 110 

volts. From £1-80 (36/-). 



PRECISION MINIATURE SOLDERING IRONS 

Antex. Mayflower House, Plymouth, Devon. 
Telephone: Plymouth 67377/8, 
Telex: 45296. Giro No. 2581000. 

~J Please send me the Antex colour 

catalogue 
_J Please send me the following 
Quantity Model Bit Size Volts Price 



I enclose cheque/P.O./cash value 



NAME 

ADDRESS . 



PW.4 



1019 



FULLY TESTED AND MARKED 



A fill 7 


ISp 


OC170 


Ha 


AC126 


itt 


OCI7I 


Hi 


AC127 


17k 


OC200 


25p 


A CI 28 


13p 


OCSOI 


26n 


AC 178 


Sit 


'2O301 


13p 


ACY17 


lit 


'26303 


13p 


AF239 


87 p 


amaoa-i 


lOp 


AFlBfi 


Mi 


38UM-G 


25p 


AF13» 


S7p 


2N 130 8-7 


jgfi 


BC164 


Mi 


2N1308-S 


3Sp 


BC1T1-BU107 


18n 


2N13S9-FET 4S» 


BC172»BC:10H 


lap 


•2N3B44A 


Hi 


BF194 


Ub 


POWER 


TRANSISTORS 


BF274 


ISp 


QC2fl 


Hi 


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M 


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30; 


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13p 


OOM 


Ha 


BSY27 


ISp 


OC-2R 


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ISp 


ocas 


Ha 


BSY29 


ISp 


OC36 


37p 


BSA9S.4 


13p 


AD1W 


Hi 


OC41 


13p 


ACTIO 


tl-25 


OC44 


ISp 


2N30S5 


Ha 


0C4S 


ISp 


•28034 


25p 


OC7I 


tap 


DIODES 




OC72 


ISp 


AAY42 


lOp 


OC81 


tai 


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9p 


OC81D 


ISp 


OA7S 


•f 


OC139 


13p 


OAH1 


H 


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17p 


IN914 


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rncn 


Packs of 


your owf 


i choice up 


FKEE! 


to the value of SOp 


with orders 


over £4. 







RETURN OF THE UNBEATABLE P.I. 
PAK. NOW GREATER VALUE THAN 
EVER 

Full of short lead KCmiconduclors and electronic 
components, approx. 171}, We guarantee at least 30 
really ttlgb riuaiity factory marked Transistor* PNF 
and NPN. and a host of diodes anil rectifiers. Motinte.1 
on printed circuit panel*. Identification chart supplied 
to give Mime information on the tranviirtors. 



P| PLEASE ASK FOR FAK P.l. 
r I lOu 1*. £ P. on Lhis Pafc 



ONLY 



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TELEPHONE: SOUTHEND (0702) 46344 



NEW UNMARKED UNTESTED PAKS 



25 



Mixed volt« 1( imlt Zeners Top Bat 
type. 



50p 



30 



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811. In TOO can. ■ W P 

Mai series "Alloy" FSP Transistors. 



50p 



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Sll. and Germ. JVp 



100! 



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50 



ftil. Ditxlt*. sub. niin. 1SS14 in*l IXEH6 
types* 



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Experimenters' Pak of Integrated EA n 
circuits. Data supplied. JVp 

811. Trans. STN, PNP, equivalent to [A. 
O03DS/1, 2N7u6A. BSY35A, etc. "H 



10 



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50p 



20 



BY126/7 type Silicon Reetlflri* I amp 
plastic. Up to 1,000 volt.i. 



40 



250mW. Zener Diodse DO-7 rnin, 
(liana Type. AV',40% Good. 



50p 

SOp 



COLOUR T.V. LINE OUTPUT TRANS- 
FORMERS, Designed to give 25KV when used 
with HL509 & PY5Q0 valves. As removed from 
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ONLY £1 each. Post & Packing 13 p 



NEW TESTED & GUARANTEED PAKS 



SOp 



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1N4007 Sll. Rrc. Diode*. 1,000 P.LV. 



SOp 



SOp 



2BSP5 Light Sensitive Cells. Light Kes. rf\_ 
400 fi Dark IMfi 3Up 



B9IO SKT163.HU PNP Genu. 
** equivalent to OC44, OC4S, 



50p 



NPN. Sll. Trans. A08 BSX20 9H934S 
500 MHi, 3S0mW. 



50p 



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50p 



1 "' '' 200 i *i ie ^ Capacitors, Post and packing 13p Cfln 
vw Appror, Qaantlty eounted by weight. J "p 



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tv ACISS, OC31/2. OC71/2, NK271, etc. ■ )U P 



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*"■** A pprox. Quantity counted by weight. "'H 



Aft Wirewoiind Resistors. 
^* Postage 7p. 



Mixed Values. 



50p 



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Resistances. 

Post & Packaging 25p 



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LOW PRICE, HIGH QUALITY SPEAKER SYSTEMS 



All cabinets are new and carefully designed acoustically with speakers mounted on 
speakers ate ex-TV high quality with hi-flux magnets carefully matched and tested. 



chipboard bafflsi 



ADASTRA DOUBLE 




S stereo solid state amplifier housed in handsome cabinet 
veneered in natural teak. Sire ll| x 6 x S^in. 10 Transistors- 
power output 5 watts peak per channel. 22Q-240v A.C. Output 
impedance 12 to I S ohms (ourCowdrey speakersystem eminently 
suitable). Smart blue escutcheon. £14,70. P. & P, SSnp. 





CARTRIDGES 



Stereo: Sonotone 9TA H/CDiamond £2.40. Ronetce S10S Medium 
Output, £1.40. SI06 High Output £1,40. Acos GP93 I Sapphire, 
£1.90. GP94 I Sapphire, £2. TA700 equivalent to B.S.R. SXIM 
£1.75. Japanese equivaienc to B.S.R. TCos. £1.75. P. & P. 7np 
on each. 



CAXTON COLUMN 

This is a column cabinet 23| x 51 x 5£in. 
deep finished in black or woodgrain cloth 
with blue or grey Vynair front. Keyhole 
slot for wall mounting. Fitted with three 
speaker units. 9 ohms impedance. Handles 
8 watts. Makes alt the difference in quality 
and volume of tape recorders and record 
players. Real bargain at £2.?S. P, & P. SSnp 
each. 



BROADWAY ELECTRONICS 

■1 MITCHAM ROAD, TOOTING BROADWAY, 




ELF 

An extension speaker of 

quality, 9 x Sj x 3jin. 

veneered in natural teak 

with smart gold and 

mottled Vynair front 

3 ohm speaker. The 

baffle is half inch thick. 

A real bargain at £1,90. 

P. & P. 30np. IMP 

Wedge shaped extension 
speaker 7± x 6| x 4in. 
(max.). Covered in wal- 
nut wood grain cloth 
ith mottled Vynai ' front. 
Keyhole slot at back. Fitted 
th 3 ohm speaker unit. Only 
£1.25, P. &i,P. 30np each 

THE l=!ESTA 
£2.95 

P. & F. 30np. 
Brit. Isles. 
Fitted with 7 
x 3 i peaker 
and Volume 
control. Teak 

veneered with Black Vynair. 
10" x 7J," x 3f* deep. 3 ohm ex TV Speaker. 
TRANSISTOR SPEAKERS 

3 in. 35 ohm. 50np. p. & p. 7np 
SPEAKERS 

E.M.I. I 3i x 8in, 3 ohm £2,50, 15 ohm. P. & 
P. 30np. E.M.I. 3tn tweeter Mnp. I s . & P. 
lOnp. E.M.I. I3i x Bin. fitted twj 2,in. 
tweeters, 15 ohm £4.50. P. & P 30np. 
E.M.I. I3± x Bin. (IS ohm) Hi-Fi quality 
£4.25. P. & P. 30np. E.M.I. Crossover 85np. 
P. & P. Snp. Bakers 12 in. 25 wati. B and 
IS ohms £7. P. & P. 30np. Eagle crossover 
90np. P. & P. Snp. Xtal lapel Mike 40np. 
P. & P. Snp. 

Tel. P.U. 6Snp. P, & P. 5np. 
Tooting Broadway Underaround Station) 
LONDON S.W.17 01-172 JS84 (C/osed aW day rVe.mexday) 




SPEAKER HATCHING 
TRANSFORMERS 

3, 7, IS ohms, 8 watt, 70np, P. & P. 
ISnp. 

VYNAIR 

Widths from 40 to 54 in., 75np yd. off 
roll. P. & P. lOnp, i yard 40np. P. & 
P. I On p. Send 5np stamps for samples. 

MONO 

GP.9I Stereo Compatable £1.25. 
Acos GP67/2 will replace Collaro and 
Garrard Mono cartridges, 95np. 
T.T.C, Crystal High Gain. 75np. 
B.S.R. TC8H Jap. equivalent £1.25. 
P. S P. 7np. 

The 

SHELLEY, 

Size 21 x 1 1 x 
6iin. 

An extremely 
elegantspeaker 
system made 
of 12mm. chip- 
board covered 
with teak lea- 
thercloth with 
mottled 
Vynair front 
This unique 
system uses 
three ex TV 
speakers. 
Carefully 
matched and 
tested. Will handle 10 watts and 
will match 8 ohms impedance. If 
preferred the speakers can be wired 
in series parallel to match 3 ohms 
impedance. A real bargain at £4,95 
plus 6Snp P. & P. MATCHING 
TRANSFORMER for IS ohms 80np 
post free. 




1020 



and it need only be set once and left. If the actual 
resistance of the meter is known (to 1% accuracy), 
then VR1 and R9 could be replaced by a single 1% 
resistor to bring the resistance up to lOkfl. However 
the present arrangement might still be preferred for 
economy. 

An additional resistor R8 brings the series resist- 
ance up to 20kU, giving IV f.s.d. Division of any range 
by two (i.e: doubling the meter deflection) is achieved 
by pressing S3 which shorts out R8. 

The IV, 10V, 100V and 1000V ranges are selected 
by SI. On the IV range (0-5V when S3 pressed) the 
base of Trl is connected directly to the positive 
measurement terminal. For the other ranges, 
appropriate divider resistors are selected by the two 
sections of SI. The input impedance of the instrument 
varies with the range selected, partly because the 
aim has been to use inexpensive preferred value 
resistors throughout, but it is never less that 3-5Mft. 
Pairs of resistors in parallel are used to obtain 
non-preferred values in the case of R2, R3 and R4; 
this arrangement can incidentally be shown to give 
one a statistically better chance of getting a high 
tolerance. The divider values R1/R5 may at first 
sight seem wrong for dividing by 10, but this is 
because the shunting effect on R5 of R6 and the 
impedance of Trl base has to be taken into account. 

The meter is protected from forward overloads by 
D3 which starts to conduct when the voltage across 
it is about 0-7V i.e: 140% of f.s.d. A germanium 
diode D2 is used for reverse overload protection 
since it will conduct at about 0*4V i.e: —40% of 
f.s.d. (IV). Note that the reverse overload protection 
is ineffective if the -^2 button is pressed. In the 
event of an extreme input overload of either polarity, 
it is more likely that one of the Darlington pair 
transistors (cost lOp each) will burn out than the 
comparatively expensive meter movement. 

The function switch is S2. The battery test position 
is a necessary stop between off and measure. The 
batteries are tested by halving their voltage 
(nominally 18V) with RIO and R7 and applying the 
resultant voltage via Dl to the zener diode Tr3. The 
meter measures the voltage drop across Dl. Since 
this cannot be more than 0-7V and the meter is 
giving IV f.s.d. (the -^2 is inoperative) the meter 
will not be overloaded. In fact a meter reading of 
0-6 - 0-7V indicates fresh batteries, while any 
meter indication at all above zero indicates useable 
batteries. 

In the short circuit zero position of S2, the 
measurement terminals are connected together for 
adjustment of VR2. In the off position, the batteries 
are disconnected and S2b places a short (actually a 
small portion of VR2 to simplify switching) across 
the meter movement. This helps to damp down 
oscillations of the needle if the instrument is jolted 
in carrying. 



CONSTRUCTION 

The instrument can be constructed in any con- 
venient insulated box; the author chose the heavier 
type of polythene food container (size 5 3 4inX3 1 2in 
X 2in) sold by camping shops, since its flexibility and 
the shape of the removeable lid gave some physical 
protection for the meter. There is also spare space 
inside which in practice proves useful for storing the 
test prods. 

The components are wired on a small piece of 



15in matrix Veroboard. There should be no diffi- 
culty fitting them on if the miniature types specified 
are used; the complete layout is shown in Fig. 5. Note 
that one conductor track is removed completely from 
the Veroboard, using a razor blade, and 17 breaks 
are made in the remaining tracks. The board is 
secured by four 8BA bolts to the box lid, with a piece 
of scrap foam rubber or polystyrene as a spacer 
(see Fig. 6), together with the meter, switches and 
terminals as shown. Before mounting, check that all 



Veroboard 




,1" n n nm 

Ezra 



'UMinuum 



Scrap polystyrene / 

or foam rubber oqa 

Hardware"" 



Fig. 6 .- The method used for mounting the component board, 

these parts will fit together on the lid and allow the 
box to close; in the prototype it was necessary to 
trim the Veroboard slightly to clear the adjacent 
switches. The two batteries can be taped in any con- 
venient position as they do not need frequent re- 
placement. Two holes are made in appropriate 
positions on the box to allow adjustment of zero 
controls VR2 and VR3 from outside using a long 
screwdriver. 

It is difficult to apply lettering direct to polythene. 
The panel labelling shown in the photograph was 




An internal view of the completed high impedance voltmeter. Compare 
this with Fig. 5. 

done by putting Letraset letters on white contact 
adhesive sheet (Woolworths) which sticks well to the 
box. 

The meter scale is already labelled 0-50 which 
allows direct reading on ranges with the -s- 2 button 
depressed, but is less appropriate for the IV, 10V, 
100V and 1000V ranges. For these a 0-1 scale can be 
added to the meter after removing the plastic face 
of the meter by gently pulling it away. 

CALIBRATION 

With the function switch at off, zero the meter by 
means of the screw on the meter front. This is purely 
a mechanical adjustment of the movement and must 
not be used instead of the electrical zero controls. 
Switch to measure and, with no input, adjust VR3 

1021 



for zero meter deflection. Then switch to short 
circuit zero and adjust VR2 for zero. Initially it may 
be necessary to adjust VR3 and VR2 more than once. 
The calibration control VR1 can now be set. This is 
best done by connecting the voltmeter to any voltage 
in its range with a meter (any impedance) of known 
accuracy in parallel with it, and adjusting VR1 for 
corresponding readings. It is possible, though less 
easy, to set VR1 without any other meter. This is 
done by connecting the instrument to any voltage 
source that will give about 40 to 50% deflection on 
any range, and successively adjusting VR1 until 
pressing the + 2 button exactly doubles the deflection. 
USE 

The function switch allows a quick check of the 
battery condition and the two zero settings every 
time the voltmeter is brought out for use. Once set 
accurately, VR1 should not be readjusted. It is 
necessary to readjust VR2 and VR3 occasionally, 
particularly with temperature changes. Allow a few 
seconds for the zero settings to stabilise when first 
switching on the meter. 

The usual rule for meter usage should be followed, 
namely: select a higher range than the maximum 
voltage anticipated before connecting the meter to a 
circuit. In practice the -^2 button proves extremely 
useful for doubling meter deflections of less than half 
scale. Remember that a meter measures most 
accurately over the upper 50% of its scale, where all 
measurements from ■ 25 to 1000V can be made with 
this instrument. It is important that the Veroboard 
and switch wafers be kept clean and dry if measure- 
ments above about 500V are to be made as tracking 
problems could otherwise arise. 

The impedance of the meter is high enough for 
confident voltage measurements in virtually all 
common circuits, except some high impedance valve 
grid and f.e.t. gate circuits. Unlike a moving coil 
multimeter, the impedance is virtually the same on 
all ranges. 

It is possible to use the meter in a centre-zero mode 
for detecting d.c. nulls in bridges, etc. Set the 
function to measure and adjust VR3 for exactly half 
scale deflection, then switch to short circuit zero and 
adjust VR2 for the same deflection. The meter will 
now indicate voltages of either polarity at the 
terminals, the needle swinging to the right for a 
positive voltage at the positive terminal. The voltage 
swing over the whole meter scale is not changed, 
and the + 2 button is still operative. 

The batteries have a fife of many months in normal 
use, or about a week if the meter is left on con- 
tinuously. The instrument can in fact be operated 
on seriously run-down batteries, although the zero 
settings will drift badly. ■ 



TELEVISION 

We are pleased to inform readers that our sister 
journal Television has now resumed publica- 
tion following settlement of the recent printing 
dispute. 

Issue dated February 71 was published 

on February 12 
Issue dated March 71 will be published 

on March 8 
Issue dated April 71 will be published 
on March 29 
We apologise to readers of Television for the 
loss of the December 70 issue and late appear- 
ance of subsequent issues. 




ElectronoteSoo 




S.GINSBERG 



COMPUTERS have been with us for some time 
but many people do not realise the degree of 
sophistication which is now being achieved. A 
fairly recent ex;unple is REDACAL. Basically a 
computer service, it enables any electronics cus- 
tomer to use a computer to solve problems. With 
REDACAL the design engineer has a powerful tool. 
He can, for example, ask this system to tell him of, 
say, an operational amplifier which has certain 
minimum and maximum gains. He might also 
specify that it must come within other limits, per- 
haps a 5V line. Within seconds, REDACAL will list 
all the currently available devices which will satisfy 
the conditions layed down and will also quote the 
current market prices, too. 

But this system goes much further than provid- 
ing such simple information. The designer can tell 
the computer what his newly designed electronic 
circuit is and seek its advice as to whether the cir- 
cuit will work properly. For example, the designer 
can ask REDAC.\L in, say, the case of a square 
wave generator, what frequency the final output 
will be if all the capacitors and resistors were 
varied within a certain tolerance. Imagine if there 
were fifteen resistors in the circuit and they were 
all 5 per cent tolerance. They could all vary and 
this would affect the circuit. Once REDACAL has 
given a circuit the OK, the designer can literally 
put the design i:ito production and know that the 
snags have been ironed out. 

How does the designer tell the computer his 
problem? Easy, he simply telephones the computer 
and uses a thing called a modem (modulator/ 
demodulator) which a standard telephone handset 
will sit in quite happily. He can also use a type- 
writer keyboard similar to the kind used in tele- 
printers. Thus any designer is no further away than 
the nearest telephone. 

An interactive graphics terminal is available for 
circuit layout work. This is really a large cathode 
ray tube on which the designer can call up various 
shapes and pieces of circuit which he can then posi- 
tion very accurately with a light pen. He merely 
touches the porton he's working on with the light 
pen and points to the exact location he wants it 
and bingo— it's there immediately. Thus a designer 
can draw out a complex mask for an integrated 
circuit. When he has finished, he can ask the com- 
puter if there is a better way of drawing it, or if 
he has made any mistakes, etc. The system can 
then be used to provide masters for actually mak- 
ing the ICs. ■ 



1022 




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— CIRCUITS AND SEE HOW THEY WORK . . . INCLUDING . . . 



• VALVE EXPERIMENTS 

• TRANSISTOR EXPERIMENTS 

• AMPLIFIERS 

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• SIGNAL TRACER 



PHOTO ELECTRIC CIRCUIT 
COMPUTER CIRCUIT 
BASIC RADIO RECEIVER 
ELECTRONIC SWITCH 
SIMPLE TRANSMITTER 



• A.C. EXPERIMENTS 

• D.C. EXPERIMENTS 

• SIMPLE COUNTER 

• TIME DELAY CIRCUIT 

• SERVICING PROCEDURES 



This new style course will enable anyone to really understand electronics by a modern, practical and visual method — 
no maths, and a minimum of theory — no previous knowledge required, ft will also enable anyone to understand how 
to test, service and maintain all types of Electronic equipment. Radio and TV receivers, etc. 



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P.W.4J 
"~023 



r 









LOW COST ELECTRONIC AND SCIENTIFIC 
EQUIPMENT AND COMPONENTS 





SINGLE SPEED TAPE DECKS 
After much effort 
we lin re obtained 
a further consign- 
ment of this 
popular single 
upei'd tape deck:. 
Complete with 
liccr I, Replay 
head*, a separate ^■■■■■■■■ssw'OBW 
erase hem] to- 

Jtelher wttn fast erase remote control 
facilities. A £' ainfcle track mi 7' Rpool.i 
I S7»cc. Three motor mains operated 
■ . l i ■ - - : l mi liny in. 11- wni;,. Hlnrk exists. 
We cannot guarantee further supplies, 
Uarfcam Price £5 88. 



NEW COMPLETE TELE. 
PHONE DIALASSEMBLIES 

Clear Perspex dials— n., 
markings. £8 88. 




KEYNECTOR 

Connects anythinK 
electrical in seconds 
without pluga or 
toctteti. No more 
worries about daneer- 
ous live wires. Nnir 

ynu can make electrical rnnnn-i 

mWv. in seconds with the ni ■■lutionary 
new Kcyneetur. Cuts nut plucs, sockets, 
ami saves time. A hundred different 
mterv in the home, anil a must for the 
lo- It -yourself enthusiast. Only £2-58. 
Or send for a leaflet. 




E.H.T. GENERATOR 

Bran. I new D.C. CONVERTER. 
Ml'LLAKD TYPE ] 04 Q 
INPUT 12V DC 3 amp. 
Ol'TPf'T 1HOOV (min) at I mA. 

•ioOOV (mini on SO LOAD. 
Full spec, and circuit provided. En- 
capsulated iiiotlule L fi". W lil". H 3 J", 
Price £5 50 (p & p incl). 



GRAMPIAN AMPLIFIERS 
Type 3H51) SOW mains input. LiM ohm 
o.'p audio power amplifier*. Onlv a few 
available. Belling well Mow the list 
price. £15 50 each cartnu- cj i™. 



MINIATURE SQUARE COUNTER 
6 DIGIT 

Ity Veeder Root, Rotary ratchet type 
adds I count (or each Sti" movement o] 
shaft. £0-80. 



BRAND NEW MOVING COIL DC 
TEST METERS 

Compact and i Ttahle. W 2 >", H ]}-. 
O 3*. In blacs, plastic ease. Availabh 
as follows: 3-tt-3 Volts. Prod on Base 
0-13 and 0-300 V Dual Range Voltmeter 
0-3 and 0- 300V "Dual Range Voltmeter 
0-7 5 Amps Ammeter. Our Price £1-75 



LINEAR THYRISTOR CONTROLLED 
LIGHT DIMMER— BRAND NEW 

HIkI) grade full 
wave bridge circuit 
Hives linear control 
"t light brightness. 
I ileal for controlling 
room lighting- and 
a.c./d.c. commuta- 
tor motors fitted to portable eiectrie 
hand drills. Fits standard 'I'm. com In it 
box. 'JAW. uC'Hz, 40(1 IV. Price £310. 




RESET TIMERS— ACRO TIMER BY 
HAYD01T 

Synchronous motor driven timer pro- 
viding manual adjusted delav. Delay 
i:mi- is set on Kraduatcd dial. Press 
button closes contact ami drives motor 
wnich drives ao arm until II actuates 
the load switch. The cam then returns to 
initial position for repeat act loo. Various 
range* available. 230 V 50 Hj Load 
contacts 15 A 2 SOS- 



RIGHT ANGLED GEAR BOXES 

Cear boxes give a drive of 
1-1. 7: 1 at right auglen to the 
input. Driveable through the 
1/p Hhatt only. Pi mens Ions 4* 
wide, 31' deep, 4J" high. 
Robust construction In cast 
iron. Price £2 98. cart. £0-75. 




Suitable lor totaling tranimitter serial*. 



MULTIMETER TYPE CT47IB 

l-'ully transistorized 
mull I range instru- 
ment for measurement 
iif vnltnge up to 1000 
MHz (IBOO MHz with 
reduced accuracy J and 
current up 2 kHz and 
f-K" ri-sistance. AC and 
DC collage and current 
ranges. AC/DC volt* 
AC/DC current 




h .1 



I -200 v. 



!2mV 
U.A-1-HA. DC 
istance 5 ranges 111 ohm-1000 M 
Dam*. R.p, voltages. !i ranges 40inV to 
•IV. Battery powered. Offered in 
excellent condition. Tested before 
despatcli. C/w handbook. £54 00, 
carriage £0-50. 



NUMICATOR PRICE LIST 
Em) Reading (OSIOM/fJ (Clean 
(tHttHlily Prire ear* Uttl basf\ 
1-3 £140 

4-10 £136 

£130 
£130 
#63 £0 SO each. 



20-100 
Met Bav. 1 
Side Reading 
XN3/FA 
XS3/F 
XN3A/F 
XS'SV 
XN11/F 
XN23/FA 
1-3 
4-10 
11-25 
2(1-100 



38m/ni Lead 
38m fm lead 

fill i /in Lead 

Kni/m Lead 
38in/m Lead 
HMm/ui Lead 
£1-15 each 
£1-10 each 
£1 OS each 
£0 B5 each 

All Post Free 



(Amber) 

I Red) 

(Red) 

(Clear) 

(Red) 

(Amber) 



BATTERY-OPERATED 
TRANSISTOR TESTER— NEW 

Type H-J'.:!!!;) for checking leakage 
current and gain current of pnp tran- 
sistors. Audio u/p Meter for calibration 
purpoirs. Price £50. 



ELECTRIC CLOCK MOTOR 

NEW 200--2.MV, 50 Hz, aW. Synchron- 
ous induction motor. 2 revs, per hour. 
0,'P shaft, iin. dla. x Jin. long. Clock- 
wise rotation. Three-holed mounting at 
1\!0° on oj„ pcd. Price £125. 



UNISELECTORS 
New ii Bank 35 way 50 V 73 Ohms Make 
before break. Half circle tvue— 2 sets ol 
wider amis at 180°. PRICE £3 13 

Miniature Ijiisulecnir 3 Hunks i'J Wav 
12V 35 Ohms. PRICK £5B5. Packing 
and postage free. 



RAPID HEAT SOURCE 



In. 1. 1 i.mn.l ui » Intra Red Tubular 
Quartz Lamps. Ideally suited as heat 
source for Drying Ovens. Egg Hatcning. 
Incubators, etc. 244V, 1.440V, 20,000 
Angstroms. Length ]21ti X Jin. dta. 
Price £1.00. 



MEMORY CORE STORES 



42 X 52-2 K bit 

ierrlte core 

store cnmplcli 

Ith H 40A 



lo«d 



diode 



Ideal for build- 
ing coinuutir 
store or hohl- 

ing Informal ion 

£2-83 post tree. 



binary lunn. l'r 



ELECTRONIC BROKERS (Dept. P.W.) 49-53 PANCRAS ROAD, 
LONDON N.W.l Tel. 01-837 7781 Telex. 267307 



1024 



OPEN MON-FRI,9-6pin 




Rx/IND APN-9 

This is a combined swt :uned Rx and CRT Ind unit, the Rx section 
tunes approx. 1. 8 to 2 Mc/s, uses tube 3BPI 3" green screen and 
34 valves of the following types, 6SN7, 6SL7, fiH(J, SY3, 6SK7 
6SJ7, 6SA7, VRI05, 6Y6, 2X2, 6N7. also lOOKc xtal, Mu Metal 
shield, po£s, swts, etc. Complete in case size 20 x 12x8" supply 
required I ISv 400 c/s supplied new with magnifier, visor and circ. 
These units are well suited to scope conversion. 

Price £8 plus 75p carr. 

TUNING UNITS 

Type R.F.26 units thesu tune 50 to 6S Mc/s but can be modified 
up to 100 Mc's fitted slow motion drive as 3 valves, I.F. O/P 7 Mc/s 
can be used with Rx that tunes 7 Mc/s supplied with circ good 
condition. Price £2.10 plus 40p post. 

Rx UNIT 3645 

This item is tor use with the above RF unit or 24 unit, as 7 Mc/s 
I.F. scrip with Det and O/P as high cycle P.U. requires 250v H.T. 
80 Ma, — I50v bias and 6.3v, complete in case supplied in used 
condition. Price £1.50 plus 75p carr, 

TEST SET 210 

Test unit for above RF unit or any equipment in range 20 to 85 Mc/s, 
this is a test osc that ;overs this range in 4 bands also as noise 
generator with 50 Ma neter, large 5.M. dial 3 section Ae, 2Mc/s 
xtal check, requires 251v H.T. and 6.3v, supplied in case in good 
condition with cal charts. Price £3.25 plus 65p carr. 

METERS 

270 Deg. meter, meter Hi" sq. basic movement 1.5 Ma, also available 
6.5 Ma fitted range anil on/off swt. Calibrated in Radio Altitude 
ideal for Rev. counters, supplied in new cond. 

Price BOp plus I5p post, 

AMPLIFIER TYPE 1962 

l/P 20O/250v 50 c/s this is A.F amp in table cabinet, with 7 valves 
inc. push pull 6BW6, unit is fitted into monitor speaker and n.eter 
for monitoring valves. Main O/P is 600 ohm fitted on/off swt fuses 
etc., case siie 19 x 12 x 10", Good basis for 10 watt amp with 
suitable o/p trans. Supttied in used condition. 

Price £4 plus 50p carr. 

SPEAKER UNITS 

Portable speaker in cabinet, size 18 x 18 x 6* fitted H.D. 8" unit 

3 ohm also 600 ohm line matching trans and lead, supplied in new 
condition. Price £2,25 plus 65p carr. 

MAINS TRANS 

All 230v Pria C Cores. Type A, Sec 49Q-400-0-400-490v at 200 Ma. 
5v 3a, 6.8v 4a, 6.3v l.6;t, I2v la. Price £2,25 plus 30p. Type B.See. 
6.5v ct 5a 5 times will give to 32.5v in 3.25v steps at 5a, Price 
£1.60 plus 30p. Type C.Sec 50v la. 6.3 ,3a. Price £1.25 plus 25p. 
Type D.Auto 1.6 KVA tapped 190, ISO, I IDv, Price £4.50 plus 50p. 
Type E.Sec I2v 1,5a, Price 55p p.p. Note type D & E not C. core. 
All trans in good condition. 

MISC. ITEMS 

Osc. unit with valves l2AT7x3, EF9lx2, LA2 pot core, jack sk. 
coax sk, 10 and 500K pats etc., new 70p, RF24 unit swt. tuned 20 
to 30 Mc/s with circ. can be used with 3645 Rx above as 3 valves £1. 
O/P and Test unit modurn unit with 2 vinkors 4 5*1 P.N. P. transis, 

4 miniature relays coil Lk 2p c/o diodes, min. valves, etc., new85p. 
Meter I Ma edgewise scale Lin to 2000 yds, size 3 x I x 3±", 
tested £1, E.H.T. smooth cond. pual type .1 and .5uf 2Kv wk size 
4 x 2 X 2" inc. term, liOp. Tube type 3BP1 with base and Mu Met 
shield 3" green screen ideal scope used with connections ex equip. 
Price £2.50p. Control unit with 2 500 Ua basic movement meters 
3 yax swts. pots, close lol res etc. new £2. Mod. Kits with 8 group 
boards with approx 130 conds and res good quality, new boxed 80p. 
Handset G.P.O. style v^ith press to talk swt in handle new, £|. 
Valves 6SN7 ex equip 5 for 50p. Amplifier A 14 1 3 l/P 230v with int 
P.U. as 6V6 amp 600 ohm o/p in case used cond. £2, Min plugs and 
sks 18 way I5p, 14 way lOp. Control panel wkh 15 min pots I meg, 
I00K, IK all i shafts en equip, 65p. Circuit Diagrams. 1392 Rx. 
1475 Rx, 30p ea. Scopes Sol CDS I 3.2 set of 3 circs, £1.50. I3A, 50p. 
Dumont 208 and OS-8. 50p ea. C.T38 Multimeter. 50p. 

All the above prices inc. carr. or post. S.A.E. for list or enquiry 
Carriage charges apply mainland only. 



A. H. SUPPLIES 

57 MAIN ROAD, 
SHEFFIELD S9 5HL 



Ill 

I 

I- 



N| * f % 1 8 Ik 

** 1 ? i 1 J % f 




MONTHLY 
NEWS 



THE first report for this month comes from 
new reporter Steve A. Money of Southsea. 
Steve has a Lafayette HE-30 receiver and a 
50-foot long- wire antenna. He was lucky enough to 
be able to use a digital frequency meter to check 
the frequencies. 

4110 Urumchi, China in Chinese at 2040. 

4685 Irkutsk, Siberia in Russian at 2054. 

4765 RTV Congo, Brazzaville in French at 1740. 

4770 ELWA, Liberia in English at 0620. 

4780 Djibouti (RTF), Afars & Issas, French, 1745. 

4785 Kunming, China in Chinese at 0010. 

4785 Baku, Azerbaijan in Russian at 1830. 

4795 Ulan Ude, USSR in Russian at 0015. 

4800 YVMO, 'R. Lara', in Spanish at 2330. 

4815 Ougadougou, Upper Volta in French, 2220. 

4823 Hanoi, Vietnam in Vietnamese at 2230. 

4850 Nouakchott, Mauritania, in French at 2215. 

4885 Novosibirsk, USSR, in Russian at 2350. 

4890 VLT4, P. Moresby, Papua in English at 2030. 

4900 YVNK, 'R. Juventud' in Spanish at 0005. 

4907 Phnom Penh, Cambodia, Cambodian at 2300. 

4940 Abidjan, Ivory Coast in French at 2225. 

4945 HJDH, <R. ColosaV in Spanish at 0715. 

4955 HJCQ, C R. NacionaV in Spanish at 0015. 

4965 HJAF, 'R. Santa Fe' in Spanish at 0700. 

4970 YVLK, 'R. Rumbos' in Spanish at 2350. 

4975 Yaounde, Cameroon, vernacular at 2115. 

4980 YVOC, 'Ecos del Torbes' in Spanish at 2310. 

4980 Ejura, Ghana with African music at 2200. 

4985 R. Malaysia, Penang in English at 2345. 

4994 Omdurman, Sudan in Arabic at 2130. 

5035 Bangui, Cent, African Rep. at 2140. 

5042 Bissau, Port. Guinea in Portuguese at 0035. 

5051 R. Singapore in English at 2330. 

5055 Chita, USSR, unknown language at 0045. 

5095 HJGG, 'Accion Cultura' in Spanish at 2320. 

John H. Saunders of Paekakariki in New Zealand 
sent in an interesting report on what can be heard 
in that part of the world, his log included: 
5054 R. Singapore, English news at 1130. 
6035 R. Monte Carlo in Italian at 0700. 
6085 DMR24, Munich, Germany, Home See. at 

0600. 
6090 R. Luxembourg heard at 1730. 
6540 Pyongyang, N. Korea in English at 1900. 
9640 R. Kuwait with news in English at 1839. 
9680 TWR, Monte Carlo in German at 0905. 
11680 BBC, London in Swahili at 0330. 
11765 SBC, Berne, Switzerland at 0600. 
11765 ETLF, Ethiopia in French at 0400. 

Graham Close of Diss in Norfolk is a new reporter 
and his equipment consists of a GEC 5-valve domes- 
tic receiver, a 75-foot long-wire and a TV antenna. 
His log included the following: 



THE BROADCAST BANDS 

Malcolm Connah 



Frequencies in kHz • Times in GMT 



3338 Radio Mozambique at 1200. 

5058 Radio Tirana, Albania at 2130. 

6125 Voice of America with news at 0245. 

6230 Radio Tirana, Albania at 0500. 

9525 Polish Radio in English at 1645. 

9625 CBC, Radio Canada in English at 0740. 
11620 AIR, Delhi in English at 0900. 
11710 ABC, Australia, sign^off in English at 1000. 
11720 R. Trans Europe in English at 1000. 
11795 WINB, Red Lion, USA in English at 2130. 
11815 TWR, Bonaire in English at 0900. 
11865 R. Trans Europe, Portugal at 1400. 
11950 NHK, Japan with sign-off at 2130. 

Colin Elanchard of Sutton Coldfield used his 5- 
valve domestic receiver and 50-foot long-wire to 
hear the following: 

6025 Radio Portugal noted at 0210. 
9660 Radio Kiev, Ukraine in English at 0100. 
9805 Radio Cairo in English until 2300. 
11765 ABC, Australia, Sports News at 0830. 
11955 BBC, Far East Relay, Tebrau at 1815. 
15320 Radio Nederland, Bonaire at 2015. 
17710 Austrian B.S. in German at 1400. 
17720 WINB, Red Lion, USA in English at 1815. 
17740 BBC, Atlantic Relay, Ascension Is. at 1815. 

John Young of Oxted in Surrey has a Pye domestic 
receiver which is 18 years old and 5 feet of mains 
flex as an aerial, with this combination he was able 
to hear: 

5990 CBC, Radio Canada in English, 0715-0745. 
6020 Radio Nederland, Hilversum, English, 0930- 

1050. 
6025 R. Portugal in English, 2100-2130. 
6135 HCJB, Quito, Ecuador in English, 0730. 
6165 SBC, Switzerland in English at 1430. 
7240 Voice of the Palestine Liberation from 

Baghdad, Iraq in English, 1900-1920. 
7250 Vatican Radio in English, close at 2055. 
7275 RAI, Italy in English, 1935-1950. 
9625 Radio Sweden in English, 1100-1130. 
9635 R. Baghdad, Iraq in English at 2010. 
9715 R. Nederland, Bonaire in English, 0800- 
0920. 
11735 Moroccan R. & TV, in English, 1700-1800. 
11740 ABC, Radio Australia in English. 
11750 BBC, Far East Relay, Tebrau at 1815. 
11810 R. Berlin International in English at 2000. 
11965 Deutsche Welle in German with close at 

1810. 
15235 BBC, Atlantic Relay, Ascension Is. at 1700. 

All reports, which should be in frequency order, 
must arrive by the 15th of the month. They should 
be addressed to the author at 5 Ranelagh Gardens, 
Cranbrook, Ilf ord, Essex. 

1025 







ui 

i 

h 

2 
D 

IT'S been a fantastic month for the l.f. types with 
DX romping in from most parts of the globe. 
The hi. bands have provided some goodies but 
twenty has developed its habit of dying rather early 
in the evenings. Ten metres is doing well but appears 
to be mostly North America. One solitary log arrived 
for two metres but surprise, surprise, someone sent 
in a 70cm log. 

Details received about the WAB contests for 1971. 
These are: 14/21 /28MHz March 14 (phone), March 
28 (c.w.); l-8/3*5/7MHz April 4 (phone), April 11 
(c.w.); v.h.f, phone contest, June 20, any frequency 
above 30MHz. More details from C. J. Morris, 
G3ABG, 24 Walhouse Street, Cannock, Staffs. 

N. Richardson (Bucks.), tells stories of a 46- 
element beam at 32ft. feeding a Garex 70cm. con- 
verter with a 9R59DE providing the eventual audio. 
Nick says that the crystal he is using is a bit near 
Channel 1 TV frequency and the result is nasty 
happenings on next door's telly. Despite this he 
managed to log six counties in one session. Call 
signs heard were: G3GWL, G3KPB, G3LQR, G3VZV, 
G8ACN, G8AEX, G8APZ/P, G8ATS, G8AUE, G8BBE, 
G8BJA, G8BGQ. 

G. Richards (Isle of Wight), 4-over-4 slot fed, JXK 
converter, Mohican, sends details of calls heard on 
144MHz. On a.m. and within a range of 60-90 miles: 
G2JF, G3FSA, G3NGK, G3UNT, G3XFW, G6LL, 
G8CEI, G8CHO, G8ECK, and on s.s.b. G3AKF, 
G30UV, G3MCS. From 125-150 miles: G3DY, G3BHT, 
G3SBF, G6CW all s.s.b. 

"We had the house rewired recently which knocked 
the RX gain up a bit", says John Moore from his 
Leicester shack. John's all-band log includes: 160- 
DL1FF, DL9KRA, GM3FSV, OK1AQW, OK1JAX, 
OK1JKA, OL4AMP, OL5ALY, OL0ANU; 40-EA8HA, 
OL9LV, UL7AA, VE2APL; 20-CP6FG, CT3AS, 
FG7XT, FH8CY, FP8CS, FY7AE, Mil, OY3B, PY2PA, 
PY6HB, VE7IC, VP2AA, VP2VI, YV4TV, ZD7SD, 
ZL1AH, ZL4BO, ZM1ABO, ZS1EI, ZS2MI, ZS5EY, 
4M1A, 4U1ITU, 8R1U, 9Y4AR (all s.s.b.); 15-AX2AU, 
AX2AVT, VU2JM, W5ILR/TF, ZE2JA, 7X2ZHS, 
9H1BP; 10-AX5MF, AX6CT, KV4AD, MP4BBA, 
SV0WBB, UA9WO, YV1ACX, ZE2JA, 9K2AL. Gear 
in use is a CR100/2, a.t.u. and 130ft. long wire plus 
one pair of earholes Moore type Sharp Mkl. 

How low can you get? Not much lower than 
1 -8MHz in Amateur terms. That's just what J. Leaver 
(Lanes.) did. Jim has a homebrew (good lad Jim) 
receiver, a.t.u., 100ft. of wire round the loft and an 
earth mat 20ft. square and 3ft. deep (he's the only 
man I know who uses a spade for spring cleaning). 
Topband c.w. log reads; DL1HS, DL9KRA, GD3DB, 
GM30XX, GM3YCB, K8DBI, OK stations 1ARI, 
1ATP, 1ATY, 1DJD, 1KRS, 1MLJ, 2BFN, 2SIX, 
3KAS, 3KWO, 5VSZ, OL1AMR, OL4AMU, OL4AOK, 
OL7AOU, PA0PN, UB2CXY, W1HGT, W3ANO, 
W3GM, W8KFX, W9UCW. 

*T know my writing is terrible", comments P. 
Harris (Lines.). Deciphered Harris heiroglyphics 
inform of the following signals on 80; CT2BC, 

1026 



THE AMATEUR BANDS 

David Gibson, G3JDG 



Frequencies in kHz • Times in GMT 



DU1FH, EA8MA, EL#K/5A1, EP2DX, ET3USA, 
FP8AP, MP4TDT, ON5DO/P/AP2, TA2BK/P/1, 
UA0ADO, UF6DR, UI8LM, VE1AX, VE2WF, VE3PT, 
VP2VI, VS6DO, ZC4JW, 3V8AB, 7X20A, 8P6DO, 
9K2AL. 

C. Henderson (Kent), B40, 120ft. end fed running 
NW/SE, went s.s b'ing on 3 -5MHz. Fruits of his 
labours include; EA3QW, EA6BN, K7HNJ, KX6BX, 
LU7AAC, LX1BJ, OD5BA, OX3WX, OY2R, OZ1LO, 
VE1IE, VOIFG, V02DC, VS6DO, W2HCW, W3AZV, 
ZB2A, ZC4IK, ZM4KE..ZM4LM, 6W8DY, 9K2AZ. 

T. Thornton (Berks.) says that 80 is providing 
nearly as much DX as any of the h.f. bands. He gives 
a list of times (GMT) when to listen as follows; 
0800-1700 for Far East and Oceania, 0600 for North 
and South America and 2000 for South and East 
Africa and the Middle East. Tim's log for eighty 
reads; ON5DO/AP, C02FA, CT2AK, DU1FH, EA6BN, 
EP2TW, ET3USA, FC2LG, FC8AP, HC1RF, HC2HM, 
HC2GG/1, HK3AVK, HK6BRK, HP1JC, HT1BW, 
IRjZfWX, IS1FIC, IT1ZGY, JX3MN, K5MU, LU7AAC, 
OD5BA, OX3WX, OY2B, PJ7JC, PY7ASQ, PZ1AK, 
TA2BK/1, K2LQQ/TF, TI2CF, VE7ZM, V02JC, 
VP2MBK, VS6DO. VP2VI, XE1CE, YV5BQV, ZB2A, 
ZC4JW, ZL4NH,'* ZM2BCG, ZM2BHX, ZS1MH, 
3V8AB, 3V8AL, 6W8DY, 9K2AL and 7X20M on c.w. 

R. Mortimore (S.Wales), has an H.A.C. one-valve 
receiver plus a three-transistor amplifier. A listen on 
14MHz revealed; ET3USA, JA1KAV, KL7BK, 
KP4AST/M, VE1ASY, VE3FSV, VE7HP, VE9AT, 
5H3MB, 7Q7LA, 8P6CC. 

A. Crooks admits to lurking in Teeside but did 
a quick flit back to sunny Leicester. Stations heard on 
21MHz while sunning himself in the warm winter 
sleet include; AX2XT, AX3ZJ, MID, OA8I, PY4BO, 
VK2FU, VK5FM W5RG, WB6NVW, YV5BPG, 
ZL4HE, ZS6QD, 3V8AL, 7X2HS, 7X20M. Equipment 
used was an RA1, PR30 and 33ft. of wire draped 
round the room. 

Enter P. Beeson Esq., (Staffs.) complete with 
HA500 and 61ft. er d fed. Fifteen metre squeaks from; 
CE3JY/P/WC, ET5USA, JA3DNL, KP4DCR, KR6EZ, 
KR6IL, PJ7JC, SV1CB, VE3XX, VE6AWC, VK2FU, 
VK6WV, VS6BE, VS6DO, WA9YGT/KG6, ZL2TA, 
ZL3FO, 3V8AL, 4Z4HF, 7X20M. 

D. Robbins has been looking through a general 
list of call-sign country locations and finds that the 
UK has a nice lktle bunch from 2AA to 2ZZ. He 
suggests things like GRO for Rockall and GDO for 
the Isle of Dogs but I think FIDO would be better. 
Fifteen metre log using a CB70A and 70ft. end fed 
reads; CN8CS, CB6DB, CB7CH, EL2BA, G2MI/VP9, 
HC2HM, HR1KS, thirty seven JA's, KG4AM, KR6BD, 
M1B, VK2NN, PJ0DX, PZ1DA, TG9MD, VP7DL, 
VP9GE, YN1CG, ZL3JC, ZL3SO, ZM30H, ZP5FH, 
ZS6AXL, 3V8AL, 5U7AW, 5Z4KC, 7X20N, 9Q5DL. 



Logs for the Amateur Bands must arrive 
before the 15 th. of each month. The address 
is: 12 Cross Way, Harpenden, Herts. 



Send for your copy 
of the HEATHKIT 
1971 CATALOGUE . 
. . . it's FREE on request 



• • 




MARINE 



HI-FI AND AUDIO 






SPEAKERS 



CONSUMER 



O Q 333333 d Q 



SHORTWAVE 




Here's the bumper Heathkit catalogue for you. Read about the 
wonder and fascination of kit building . . . see in full 
colour the world's best values in Hi-Fi . . . Radio, and even 
model radio control. Get up to date with what's new in 
scientific instrumentation . . , instruments for test and 
service . . in fact there is a Heathkit for almost every 
purpose, in every walk of I rfe. A wealth of informa- 
tion is all yours for the price of a postage stamp, 
in the Free Heathkit Catalogue. 



^p- No previous knowledge of 
electronics required. 

•fc The constructional manual 
supplied with every kit 
shows you how. 

^ Building Heathkit models 
is so economic, 

^ Save up to 50 % over 
factory built equipment. ' 

^ Money saving direct from 
factory prices. 



™ HEATH (Gloucester) LTD, GLOUCESTER GL2 6EE 

(In block capitals) 

Name 

Address 



A Schlumberger Com pan)/ 

Many other models In wide range . . . 

FILL IN THE COUPON FOR YOUR 
FREE CATALOGUE TODAY. 

51/4/71 



Post Code 



1027 






MW/LW TRANSISTOR RADIO 




Complete set of parts for this BtW/IiW 
Translator Itndlo. Originally sola b» world- 
fan ions OOfDMBy as a set (or more than £17. 
Coverage ll)2-5«5r>i + 1070-1870m. 4J* 
loudspeaker, Trail idetors 3 x AFlti, OC81I> 
4- *2 OCftl. Also w :krks oH car-aerial. Full 
instruction l«>ik I2].p tree witb parte. State 
preference rett, blue or tan and give alterna- 
tive. "Requires PPT halterv. price 22Jp extra. 
.All parts £S -87 ) + 22]p post or £10-50 
folly built + BlppML 
A few left ol Super Mii Kit (see previous 
issues) at I4-BS 1+ 2-Jip post) 
fl volt 8 transistor caperhet using 3HF A A 17 
in RF and IF stagebi powered toy a two stagH 
AF amplifier uatnc: (MJSIl>. 'J s OCK1, 
Output approx. OOflltW, 




STEREO AMPLIFIER type HV— 2x3 Watts 

Fully built. On off «ep. vui. and tone eacb channel l" 
:4j > ftin. hiph. two. 2 * ECI-SH; for 3 ulin- 
speakers, double wound main trans: fixing tlanir«-- 
and base plate, suitable for crystal cart, tuner eb 

ffi.50 (*op p. a- p.,) tioo-aaov. ac. 

Superior version — separate base, treble it vol 
each channel with mono/stereo switch 75p extra 



MULLARD STEREO "DO IT YOURSELF" 

Pre-amplliler EPiiOfll £3-10 2 amps. F.P9000 ££-90 each. Power Supply EP9002 
£4-60 Control panel SB. SO or the lot for £16-50 post paid. ihioklet top $t$V post) 



MONO GRAM CHASSIS 3 WATT 

3 Wave band long-mnl-nhori. Crans., 2OO-230V A.i: 
Ferrite aerial. Uhawsls 13 i i i Sin. Oial 13 x -tin. 
Double wound maina -.rac-former .1 valve* KCI1X1, 
KF89.EBCS1. KL84. F.7.m, Price £10-6Si 
<37jp p. A p.} Output trail*, ftir 3-ohra speaker 




NEW TAPE AHI'Lll'l KK lor -1 track B.8.K. Deck TIM. Mains and output Trans. 
10" x 6- x 4" overall, Beet : B0083, K.L84. Mike ami dram Inputs. £7-85 ',50y p. & p.) 
For 3-ohm speaker. tFor -iOO-'ioOV. A.C) 



GLADSTONE RADIO 



6 PUSH-BUTTON STEREOGRAM CHASSIS 




M.W. ; S.W.I; S.TT.a; V.H.F. : 
Uraiii: Stereo Gram Two 
separate channels for Stereo- 
gMon with balance control. 
Also oiierates with two 
speakers on Badia. Chassis 
Mine; 15 i 7 x Sjin. high. Dial 
silver and black 15 x 3in. 100- 
530JI: 1S-5UI: fio-jaTaj: 
VJIF Sfi-100 Mcfs. Valves. 
ECCM, ECU 81, EF80, 2s 
KCLHB, EM84 and Beet. 
Price £19 -OS earr. paid 
With Sler.'o Decoder fitted 
£7-60 eitra. 



HW MAINS GRAMOPHONE AMPLIFIER 

HZNO, BGL83, 0. P. Transformer ( iohtn), Vol./On-oS and Tone Control. Double wound 
mains transformer. a-J x 2{ x S'tn. separate but wired to chassis, 4 s 21 x 4iin. over 
valves £3-371 iacludinu Sin. fip«,ker (£8-75 less speaker). (Post paid.) (Two less 1(1%) 

SINCLAIR AMPS & PRE-AMPS IN STOCK, 
RETURN OF POST SERVICE. 



MAINS TRANSFORMERS (200-250V AC INPUT) 

Postage in brackets. (5*3 V at '.'(A 87 Jp (10p> 
Out 250V at 50mA and H-3V at I J A. 50p (l'ijpl. 
22V at 1A + 0.3V at 2A and 25f V at 50mA 76p (17lp), 
250 V at 40mA, 24V .it I A and fi-SV at liA 62|B (l'2Jp>, 
'250 V at Bom A, 22 V at 1 A and 8 3V at 11 A 87 Jp (l'ip) 
90V at. 20mA and 1.4V at '.'00 nA 50p (12 Jp). 

USEFUL BOX M* x 31* X 1|" with fixing bracket 18Jp< Postage lOp). £1 -85 
per dozen post free. Metal with trey-green finish. 

Complete set of parts with wirii g diagram for battery eliminator to give !K)v. FLT. 
at 20-30m.a. and 1 4v. at 120 or ;;50m.a. (adjustable I. With undrilletl aluminium box 
approx. 6 -x 3 x 3", trans,, choke, two rectifier*, condensers and plugs and socket.*. 
Price £8-75 plus 25p p. A p. 

French made (AMliC) relays, '.i-contaet changeover. 6v. d.c, 6-3v. a.c, 24v. a.c. 

or 220v. a.c. Si2e of enclosing pirspex shroud 2 T (plas pins) X 1J" dia. 

Price with octal base yalvehoMer 75p (fi for £4-00) plus 12 J p post any quantity. 



66 ELMS ROAD, ALDERSHOT, Hants. 

id Doses). FL'lJi CUABA^JTEi:. Alder-h 
8.A.E. !or enquiries please. 



CHROMOSONIC SOUND 
OPERATED LIGHT 
DISPLAY 

This compact unit (size fli* X Bi* 

" high) ta connected directly across 
the speaker output ol an amplifier, it wi 
then convert audio signal* Into a spectacular three 
colour light display (3Q0 watts light' output each OOfcwjj Scnil S.A,E. 
for iurther deUll«* /III CA !*• A P* 




J'leatf edit in St/. 11 for ttcrttQMtrjtitmt* 



>:v 



BARGAIN COMPUTER 8UMPER 
JOARDS 




Manj!* Hesistors, Con- 

deiiaerB r Diodes and 
Transistors (minimum at 

4 transistors on eacn 
board) i. 

5 BOARDS TOR 120p. 
Pogt Free. 



ACQS 
STETHOSET 

Use4 but ia good 
condition. For per 
suiia] listening and 
monitoring with 
tape recorders, 
transistor sets and 
record players. 200 
ohm DO resistance, 
& it. lead. 
30p, Foatage 71p. 



CRESCENT 



RADIO LTD 

1 1 & 40 MAYES RD 

LONDON N22 6TL 

888-3206 



PLEASE NOTE 
PRICES IN DECIMALS 



TRANSFORMER 
SCOOP 



Primary 110, 2'iO, 250 v. 
fused. Secondary 220 v. at 
.'iOniA. 6-3v, st 1 amp. 
Overall ei2e 2f* i 2' x 'if 
high. 

-each 
P. & P. ISp 



62|p ?: 



MAIL ORDER 

DEPT. 

No 

MAYES RO, 

LONDON 

M33 

6TL 



CARTRIDGES 
Stereo Magnetic 
/Telelon NM33 
£3.97 1 
Tcialdring SOOH 
£7.50 
BSR Tvpe 
teplacemsnts 
TC8 Mono XTAL 

•M74 

TC88 Stereo XTAL 

£1.971 
X3H Mono Compat 

XTAL tl.37) 



450 

3,S,15 

OHM 

10 watts 

£3,B5'c«ne£-J 
p. &p.37Jp.|p-& P. 3 



150 
3,8,13 
OHM 10 1 

wai.tti;r 

8'tlual 



CHROME TV 5TAND 

28 X Sj X IBIn, himli. 'l'lvis nimlern draign T\ 
Stand M-oiilii niakc an ideal haw for a coflt-c 
table and is • luirmiin at | 62— D Fast " 5l> 



*B-\ MOTOR Rated U P t0 U5 TOlt 7}ln 

J? i' dia. Shaft -fr' long Poat 
tV'dia. aip 



SOLID STATE BLOCK MODULES 

Phono pre-ajap E1311 Input 

100k: gain 2-- ■IK max out 

3 volt: max input 50m V. 

Tape pre-amp as above K 1 31 3, 

Power amo E1314 input 1,000 

ohms gain 2MB 300m\V. 

Organ tone oac B331D tone 

freti. 200-lk. Hi output gOniW. All above modules 9 

volt. Dual flasher E1318 Mash time 1-4 sees power fi 

volt. Laiup fiv 150mA. All at £1,25 P. 4 P. lOp 



LIGHT DIMMER 




The unit tomesi complete with MK Ivotti- 
Kront Plate and Control Knob* whft" urkJ in 
place of Light Switch it will mntrol your 
rnntii lighting from, off to (uUhrl^htiJiCJ^, 
Power — up to 300 wat tsintrfiireucuwupitrfsseil 



£2.75 



rP.&P. 
7±p. 




IMPORTED PANEL 
METERS 



KA-38C IJ' I If* BO^lA, 
lOOjiA, 500)iA, liuA, 
6raA. S meter 1mA, 300v. 
All at 

Ct.475Plua6pP.4P. 




KA-85C 3 T - X 3+' 
S meter 500uA, 
All at 



&\.97±VlxnlipV.tiF. 



COMPONENT CENTRE 

S" x G" one aided printed circuit board lOp eaeh 
BY100 type rectifler 800 plv 750mA 18p each 
4-pin transistor holder* . . . . gjp each 

2f 80 ohm loudepeaker . . . 27jp each 

21' 8 ohm loudspeaSter , . . . 8Sip each 

2J' 25 ohm loudspeaker . . . . 87 lp each 
U2 battery holders {blue plastic) . . 5p each 
10 ohm w/w pots . . ., . . 18 tp each 
OC81 double heat ollps . . 2jp eai.:h 

Tape recorder rev. counters . . . S5p each 

Please include P. £ P. 



SHELF UNIT 

Two teak finish shelves on a black frame (overall 
size 28* x 25* x 12* deep). This unit is wall 
mounting. ?50d Posta 8 e 




a 



STEREO 
HEADPHONES 

AH Types 8 ohm 

wit'i in £2.37i 

DHC-tSnttrs. - £2.fl7J 
SIHI71) £4.00 

t*'J2: ii-witb volume 
"■linr ..Is on each ear £5.50 
HI) 11 '..'05 V -Good quality 
^■jth volume control* 

£8.50 
Powl IJie-2flp rtn all type*. 



GE C HATCHET RELAY No «eua/oob/07 coil— 375 q 
.t.V.. lutivntl ntLHI 3-make break contacts. 1- 
changeover. All Sew and Boxed. 30o t^h. Post 5p. 



FLICK C^r 
SWITCHES 



250 volt 3A. Single Pole i 
off. ]|* nylon Toggle, 



I7^P 

Plus Postage 5p 




compo* 
nents: 
TOO ohm 

DPDT relar witn **&&, l^F 
200v. p»T/er»0 j 0l^F400v, paper. 
B0/uF 3JJv. electrolytlCj 3 dlodea 
OC200 tranai&tor, a 2K2fl'20 
type trrmFiistor unmarked, a 
skeleton pre-sct pot, 4 pfu din 
plug & skt», 4 foot of 4 core 
bereent All housed in a b-niall 
neat metal box. Can be made 
Into many timing devices, 

+ P- A P. 

7*P 



42£p 



1028 



TAKE 2© 

JULIAN ANDERSON 

A series of simple transistor projects, 

each using less than twenty components 

and costing less than twenty shillings 

to build. 



HAVE you ever heard the ladies of the house let 
out a yell because the washing is out and it 
has been raining without anyone noticing? — 
or have you ever had to cope with soaking deck- 
chairs? Well, this month's project should put a stop 
to all that for it is a fairly simple rain alarm that will 
sound a "hooter" as soon as the first drop of rain 
reaches a sensor. 

It is of course no good having such a device unless 
you can leave it on for long periods without the 
battery running down. The circuit used here draws so 
little current in the stand-by condition that the bat- 
tery will suffer a natural death long before the circuit 
runs it down. An on/off switch has been included to 
enable the alarm to be turned off once it has been 
sounded otherwise you would have to put up with 
the "hooter" until the rain was stopped and the 
sensor dried out. 



THE CIRCUIT 

The key to the whole operation is the use of silicon 
transistors throughout with their almost negligible 
leakage currents — a germanium transistor version 
of the circuit would be operational all the time and 
obviously be useless. 

Trl is the "switch" which is triggered by the rain. 
Rainwater, although very nearly distilled water and 




Fig. t ; The circuit of the Take SO rain alarm 



therefore not nearly such as good an electrical con- 
ductor as tap-water, has a definate resistance which 
is arranged to connect between the collector and 
base of Trl. This will allow current to flow and allow 
Tr2, which is a low-cost p-n-p silicon type, to be 
biased into conduction. This in turn biases on Tr3 
and a pulse of current is passed through the loud- 



No. 24 
RAIN ALARM 



speaker. The base of Tr2 and the collector of Tr3 
are in phase and by connecting a capacitor, CI, 
between them we have an oscillator which will pro- 
duce an audio note in the loudspeaker as long as 
Trl is turned on. 

As we have seen, Trl, when switched on, sets 
up a chain reaction turning the other two transistors 
on and into operation. Rl is included, for, if Trl was 
completely switched on, damage may occur to the 
other transistors. Its inclusion only means that the 
minimum resistance between the base of Tr2 and 
battery negative is limited to 33kH. 

When Trl is off (that is with nothing between the 
probes) the only current drawn is the leakage of 
the three transistors which is so small that we can 
forget it. 




Battery +ve 
via switch 



bee e c b 
Fig. 2: A suggested component layout on a smail tagboard. 

CONSTRUCTION 

A suggested layout for the components is shown 
in Fig. 2, the three transistors together with Rl and 
CI are mounted on a tagboard. The probes can be 
made in a number of ways for it is only necessary 
to arrange for water to complete a conductive path 
between them. A sheet of plastic to which a piece 
of blotting paper has been glued with the probes 
pushed into the blotting paper works very well but 
will not last all that well. Alternatively a small piece 
of Veroboard can be used, one of the probe wires 
going to every second copper strip, the other probe 
connecting to the others. However, there are lots 
of ways for arranging for the rain-water to complete 
the circuit and with a little ingenuity you should 
be able to think up one of your own. ■ 

1029 




2ER-fl£ 



SOMEONE, somewhere, remarked that PW ought 
to consider publishing an article on a piece of 
equipment designed as a joint venture by the 
leading regular contributors. It needed only malicious 
encouragement, coupled with a subtle admixture of 
coercion, bribery and blackmail, for Mr. Eeven 
Steeven to find himself forming a small committee 
for this purpose and as a result of a second-generation 
application of coercion, bribery and blackmail, to 
discover that the following running order of volun- 
teers had agreed to join him in this formidable and 
noble undertaking. 

THE EXPERTS ASSEMBLE 

The following have arrived: 

Eric Foulpest, (G4NBG), Julius Andyman (of 
"Take 40" and "You too can build a computer for 
six and tuppence" fame), L. A. J. ("Icky") Iceland, 
Downy Arthur and Rickey Colins (founders of the 
PW Darby and Joan Club), A. S. Bricklayer (G8 and 
Bar), Rave Glibson (author of "Tahiti on a Hat-pin 
or Bust"), Salvador Hogshead (of no fixed abode). 

Starting prices: Foulpest 2/1 favourite, Andyman 
5/2, 100-8 the field. Arthur and Colins wear blinkers. 

The following declined to support the project for 
reasons too numerous and scandalous to men- 
tion: Mr. F. Greyer, Q. Cameron-Highlander, Randy 
Lester ("The Electronic Entrepreneur"), J. Thornton 
Lawrence of Arabia and Aberystwyth (henceforth 
referred to as J. T.), Malcolm Conman ("DX on a 
G-string"), B. F. Gravyboat (author of "Up the 
Spout"), F. C. Judder and M. Wallis-Collection ("The 
Testm aster in sickness and health"). 

1030 



A special sub-committee was also formed to liaise 
among themselves and with powers to mind their 
own business. This comprised: Henry (to make rude 
remarks), Pax (to do the doodling), Maxwell (to 
make the coffee) and the office boy (to sweep up 
spare committee members). Components were 
obtained from Steptoe's Surplus Stores. Gowns by 
Renta-Rag Ltd. 

MOMENTOUS DECISION 

At the first meeting Mr. Steeven appointed Mr. 
Steeven as Chairman of the Committee with sole 
discretionary rights to abandon the project at the 
slightest provocation. The Committee then adopted 
the motto Nil Nijinsky which, for the ignorant is 
an allusion to the ancient precept that a camel is a 
horse designed by a committee. 

During several sessions, each followed by a 
"session", various proposals were put forward — and 
then pulled back. Messrs. Colins and Arthur sug- 
gested that if it was not going back too far the 
committee might consider resurrecting a classic 
receiver design of the early '20s. The Chairman 
asked if they meant the 1820s or 1920s. 

Mr. Iceland was soon up in arms at the idea 
remarking that readers would probably take such a 
set to be an Ancif:nt Monument. However he would 
agree to any other suggestion provided it was for 
a disintegrated digital clock using nine NAND/AND 
and four EITHER/OR TTLs with positive flip-flap 
readout, which he happened to have in his junk 
box. During questioning Mr. Iceland agreed that he 
had the copy ready for such a project but had 
hesitated to submit it to the Editor fearing it might 
be below the usual standard of material in the 
magazine. 

The Chairman remarked that nothing could be 
lower than the present level. (Applause and cries of 
"Resign"). 

COST FACTOR 

Mr. Andyman supported Mr. Iceland's project with 
the proviso that the total cost to the reader should 
not exceed 20p. Nor should it use more than 20 
components. After allowing for the nine NAND/AND 
and four EITHER /OR TTL's it should be possible to 
complete the design with not more than seven other 
components. Mr. Ineland's remarks are not recorded 
but it is understooc. that he muttered something about 
£200 and 2000 somethings. 

Mr. Hogshead also approved of the disintegrated 
clock concept provided he was allowed to design the 
peripheral hardware for the necessary testing of the 
clock. He was prepared to completely re-design and 
up-date his VCR97 oscilloscope, his ultra-linear wide- 
band total distortion amplifier (EF50-EF50-EF50 
EF50-PX4-PX25-DA100) and his guitar amplifier 



I 



which he had never got around to using anyway. Off 
the record, the walls of his flat had caved in and 
collapsed when he first turned up the wick on the 
SOW job but his wife had blamed it on the Concord/ 
Concorde (this is for our French reading reader). 

THE TENSION MOUNTS 

At the 54th. session of the Committee it was 
reported that the Editor was getting a little nervous 
and impatient after waiting so long for the promised 
article and anyway he was constantly complaining of 
cramp in Ms fingers from the signing of the steady 
stream of allowance claim forms from a slightly 
unsteady Committee. The Art Director reported that 
so far he had not received any instructions on the 
artwork for the article. 

Eric Foulpest thought that the clock idea was "all 
right" if the output of the clock could be used to 
drive a series of lOkW power amplifiers to radiate 
time signals at the bottom end of each amateur band 
from I ■ 8 to 2300MHz for 24 hours a day. It was also 
desirable, he said, to be able to direct the output of 
all the amplifiers onto the frequency of any pirate 
station in any amateur band. 

He was willing to accommodate the entire equip- 
ment at his own QTH in return for which service he 
would expect to be allowed to use the equipment 
during contests with the power input reduced to 
150W of course and to 10W on Top Band, naturally. 
(He's got to be joking! Ed.) Mr. Glibson commented 
that after listening around the bands recently it 
would be all contests and no time signals. 




This excellent shot reveals the Ingenious hybrid circuitry of the 
"Super-Fet". The familiar ST2-TD2-ZD2 line-up is followed by a 
DITT02U2 audio gain-block located in the very centre of the layout, 
The plug-in power supply can be seen in the bottom righthand corner. 
The signal input attenuator Is at the extreme left centre, (Photographs 
courtesy PW Space Centre), 



THE BIG RE-THINK 

At the 73rd. session Mr. Glibson submitted that all 
previous proposals should be forgotten and a fresh 
start made. The Committee agreed and went to lunch, 
then tea, then supper and so to bed. 

Mr. Colins admitted that he had not really been 
paying attention at the previous meetings being 
mostly pre-occupied with his love life and his new 
house. He volunteered to write an article describing 
a bed, a vast bed, with a giant console from which he 
could control all the curtains, all the doors, all the 
radios and the TV's not to mention the tea-maker. 
Trouble was that he'd have to get out of bed to 



service the equipment but he was working on that 
problem. 

The Chairman interrupted Mr. Colins to remark 
that if Mr. Colins cared to submit his plans . . . but 
Mr. Colins cut in to say that he was not going to 
submit his plans to anybody especially as he was 
getting married soon. 

Mr. Bricklayer arrived in time for the 99th. session 
of the Committee and apologised for his absence from 
the previous meetings. Without any further ado he 
proceeded to outline briefly the circuitry for his 64- 
dollar (sorry-transistor) Super-Fet All Band Receiver. 
Four hours later the Committee approved the design 
for publi cation without further discussion. 
Circuit 

The circuit is the same as the physical layout 
which can be seen in the photograph of the Super- 
Fet. 

CONSTRUCTION 

The layout is the same as the circuit which can be 
seen in the photograph of the Super-Fet. The only 
component worthy of comment is the band switch 
which has the following positions :- 

Band 1. Vienna Philharmonic. 

Band 2. Foden's Motor Works. 

Band 3. Plastic Ono. 

Band 4. Carrol Gibbons and the Savoy Orpheans. 

TESTING 

Don't bother to check the wiring, it won't work 
anyway. Connect up a 9V non-polarised battery, stand 
well back and switch on. Go out and buy a kit set. 

CONCLUSION 

If you want to do an article for PW but can't think 
of a subject, dream of all the things you'd like to 
make for yourself and then pick on something else. 
Above all else, don't make the mistake of doing this 
on April the First. ■ 



WHAT'S IN THE MARCH 
TELEVISION? 

(On sale March 8th) 

■ HELICAL-SCAN VTRs 

An upsurge of interest in videotape 
recording seems imminent. For amateur 
and semi-professional use this means the 
helical-scan v.t.r. Just what are the 
problems? 

■ DIGITAL IC's 

The price of digital i.c's has fallen very 
substantially in recent months so the time 
is ripe for their exploitation by the amateur 
constructor. A detailed account is given 
of their characteristics and their ap- 
lications. 

■ SERVICING TV RECEIVERS 

Our series on TV receiver servicing 
continues with the Decca DR100/101 
series of dual-standard models. 



1031 






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NAME. 



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POST CODE. 



51/4/71 



1032 




by GORDON J. KING 

THIS supplement is designed to herald a new series of 
articles focussed on radio and audio servicing, starting 
next month. The servicing series will be handled by col- 
league H. W. Hellyer (Mac to his mates and the author of 
the recently acclaimed Tape Recorders book by Fountain 
Press) and yours truly, and between us we shall be ex- 
ploring the theoretical and practical aspects of radio and 
audio equipment servicing, taking in the ordinary radio 
receiver as well as the more exotic hi-fi receiver (tuner- 
amplifier?) along with audio amplifiers and tape recorders, 
with Mac corcluding the series on the latter note and 
reflecting his vast experience in the fields of tape recording 
theory and servicing. 

We shall also be unweaving the enigmas of valve and 
transistor theory while introducing practical relationships. 
We shall demonstrate contemporary testing procedures, 
tell how to work out component values, delve into the 
mystery of multiplex f.m., introduce hi-fi specifications, 
have a look at pickup theory and practice; in fact we shall 
be embracing as widely as possible the entire area of 
'servicing' and in order to do just that we might well find 
it necessary to split all or some of the five parts into two 
sections to yield a desirable balance between theory and 
practice. 

Although the actual using of test instruments will be 
adequately highlighted in the series, such things as instru- 
ment basics, what instruments are available, what they 
do and how they do it, their salient features, respective 
importance and so forth will not be included. This is 
where I come in with this supplement, the plan being to 
set the instrument stage, so to speak. 

There has been little intrinsic change in instruments 
over the decade. We still have meters for measuring 
voltage, current and resistance by means of a pointer; 
and we still have instruments for generating various types 
of signal, pure tone, pulsed or modulated. The versatile 
oscilloscope is still the same. There is still the cathode- 
ray tube with its pin-point of light which, under the control 
of a suitable timebase, traces out the signal waveform on 
its screen. 



TEST METER SENSITIVITY 

Nevertheless, there has been change, but of a detailed 
rather than intrinsic nature. Change has been necessary, 
of course, to enable servicing and testing to keep abreast 
of the rapidly developing state of the art. For example, 



some of the early multimeters are now singularly unsuit- 
able for accurate fault diagnosis, testing and adjustments 
in some of today's solid state equipment. This applies 
both to the d.c. and a.c. aspects. Transistors and inte- 
grated circuits commonly run on smaller voltages than 
valves, and the currents in some of their circuits are 
remarkably small meaning the voltage dropped across 
resistive elements is also of a small magnitude. Thus our 
test-meters nowadays need to measure very small voltages 
over a substantial length of scale to maintain accuracy of 
readout. Moreover, as small voltage settings on such 
instruments reflect a reducing shunt resistance across 
the test circuit, the sensitivity of the movement itself must 
be higher than considered adequate in the valve heyday. 
Thus while we used to get by with a sensitivity of around 
1,000 ohms/volt, we now require a sensitivity of at least 
ten times that value. Fortunately, development has been 
on our side, and we can now obtain quite a fair 10,000 
ohms/volt species for a relatively modest outlay. Indeed, 
models are available up to 100,000 ohms/volt. 

Current taken by a d.c. voltmeter merely follows Ohm's 
law. For example, the resistance of a movement giving a 
full-scale deflection of 1V when passing 1mA of current 
must be 1,000 ohms. The test circuit will then 'see' a shunt 
of 1,000 ohms; moreover, it will have to yield the corres- 
ponding power to cause the pointer to swing full-scale. 
If this meter current upsets the circuit conditions the 
measurement will be in error. 

A voltmeter like that has a sensitivity of 1,000 ohms/volt 
for obvious reasons, if the full-scale deflection is geared, 
say, to 100V, then series resistance would be included to 
increase the total resistance as 'seen' by the circuit to 
100,000 ohms. But the sensitivity would still be 1,000 ohms/ 
volt. Sensitivity is enhanced only by a movement which 
gives full-scale deflection for a smaller current. A move- 
ment which requires, say, 0-1 mA (100/*A) yields a sensi- 
tivity of 10,000 ohms/volt, while a 10# A movement steps 
up the sensitivity to 100,000 ohms/volt. 



TEST METER ACCURACY 

Clearly, it pays to use the highest voltage setting con- 
sistent with a usable readout, for then the current drawn 
from the test circuit is reduced. However, working like 
that can impair the readout accuracy for two reasons. 
One because small voltages are not easy to determine 
on a highish voltage scale, and two because the inherent 
accuracy commonly tends to deteriorate at small deflec- 
tions. 

Meter accuracy is often geared to full-scale deflection. 



1033 




in 

TEST 
INSTRUMENTS 



Thus a specification of ±2% of full-scale deflection 
means that on the 100V range, say, a true 100V could 
read as 98V or 102V (the latter just in advance of the final 
calibration mark). However, a true 50V on the same range 
could read as 48V or 52V, thereby corresponding to an 
error of ±4% athatf-scale deflection. In practice, therefore, 
it is best to select a range giving the greater pointer 
deflection for the applied voltage. In that way the readout 
error is minimised. 

A common multimeter sensitivity is 20,000 ohms/volt, 
a value which satisfies the requirements for the vast 
majority of servicing tests in both valve and solid-state 
equipment. Even so, there are times when even greater 
sensitivity is demanded; when, for instance, voltage is 
measured from a high resistance circuit. Unless the 
current flowing from the test circuit into the meter is 
minimised, a substantial ratio of voltage will be dropped 
test circuit, the meter thus recording only a small ratio of 
the real voltage present without the meter connected. 

ELECTRONIC TEST METER 

When choosing a test meter, therefore, a major con- 
sideration should be the sensitivity voltage. From first 
principles, the greater the sensitivity the better; but since 
accurate meters of exceptionally high sensitivity (say, 
100,000 ohms/volt) are more costly and possibly somewhat 
less robust than their lesser sensitivity counterparts, 
some technicians and enthusiasts prefer the electronic 
test meter alternative. Such an instrument commonly 
exploits the same sort of readout (moving-coil movement) 
as the 'directly applied' Instrument just considered, 
though there are digital equivalents referred to anon. A 
major difference is that the movement is not operated 
directly from the power available in the test circuit, but 
instead from the power inherent in a valve or transistor 
circuit. In other words, the active (valve or transistor) 
circuit serves as a 'buffer' between the source and the 
meter movement, meaning that significantly less power 
is drawn from the source to work the meter. 

Prior to the transistor era, instruments like this were 
often called valve voltmeters. Even today valves are some- 
times employed, but many are now changing over to 
transistors with the advantage of battery powering and 
hence portability, A term which embraces both types is 
electronic test meter, but we might still talk of the valve 
voltmeter or transistor voltmeter. 

Valves were particularly handy for the application since 
the power in the anode circuit is controlled by voltage of 
extremely low power in the grid circuit. Stemming from 
this was a very high input resistance, established essen- 
tially by the input attenuator, which remained relatively 
high even on the lowest voltage range. Transistors of the 
bipolar type are them selves current operated (I ike the meter 
movement) and are thus somewhat less matched to the 
requirement. Nevertheless, over the years circuit artifices 
have been adopted to secure the highest possible input 
resistance; the base input, in fact, monitoring the small 
current from the test source which is then reflected as a 
much higher collector current in the meter circuit. The 

1034 



field effect transistor, which is endowed with a very high 
input resistance, similar to that of a thermionic valve, is 
now extensively used in electronic test meter circuits. 

The active circuit, of course, needs to be powered from 
the mains supply or batteries, and an arrangement is 
incorporated for setting the pointer of the movement to 
zero prior to the application of the test voltage. 



MULTIRANGE METER 

The bread-and-butter instrument is the multirange 
meter. This comes in both 'directly applied' and electronic 
form, The most common is the 'directly applied' version, 
without which it is impossible to perform even the most 
elementary of servicing operations requiring testing of 
some kind. The days of 'wet-finger' and neon bulb testing 
went out with the thermionic valve. Least complex of the 
species is for d.c. applications only; but the extra initial 
outlay for an instrument embracing a.c. ranges in addition 
to the d.c. ones is well warranted. Basic ranges are volt- 
age, current and resistance. 



RESISTANCE MEASUREMENT 

Resistance is effectively measured in terms of current 
readout, the reading being directly in 'ohms'. An internal 
battery supplies the current and this is switched in series 
with the meter movement and an internal resistive arrange- 
ment, a part of which comes out to a 'zero set' control on 
the front. When the test leads are shorted the meter is 
caused to read full-scale by control adjustment, corres- 
ponding to zero 'ohms'. When the leads are connected 
across an external resistance the meter current is reduced 
and the deflection in less, the pointer then indicating the 
approximate value of the resistance. 

This is the simplest means of resistance measurement. 
Greater accuracy calls for a special 'bridge' or a more 
sophisticated direct-reading meter. Most multimeters 
provide for at least two resistance ranges, but it is not 
unduly difficult to measure higher values than allowed 
for by the internal battery by adopting an external battery 
to give a full-scale deflection on the highest practical 
voltage range, then introducing the resistance for measure- 
ment in series with tie battery. This, though, might involve 
some sort of scale recalibration or mere scale multiplica- 
tion, depending on the nature of the instrument and the 
battery voltage. 

The greater the voltage sensitivity of the instrument, 
the higher the resistance value measureable. Very low 
values of resistance are not so easily measured in the 
manner expounded; again, a special kind of resistance 
meter is required for this. 



DIRECT CURRENT MEASUREMENT 

The voltage sensitivity reflects the lowest d.c. measure- 
able. For example, s meter with a d.c. sensitivity of 20,000 
ohms/volt would probably have a d.c. current range down 
to 50^ A (0 05mA), while a 10,000 ohms/volt meter would 
be unlikely to measure d.c. below 100,mA (all full-scale of 
course). However, it is noteworthy that this basic relation- 
ship is sometimes effected by meter movement 'padding', 
which may be adopted partly for calibration purposes and 
partly for temperature compensation, with meter overload 
protection probably having some influence. 

For testing in transistor circuits a meter of 20,000 ohms/ 
volt sensitivity reading full-scale down to about 0-1 V 






Fig. 2: The latest Electronic Avometer which operates from 
4 mercury ceils. Extensive multimeter range coverage is 
provided (see text). 



b 



5-00 



Digital 




I 



Fig. 1 : The multimeter of the future— the Digital Avometer, 




Fig. 3: The popular Taylor multi- 
meter, Model 88B with a sensitivity 
of 20,000 ohmsfvolt d.c. and 2,000 
ohmsfvolt a.c. Some idea of the 
scope range can be gleaned from 
the picture. Also see text. 




Fig. 4: Eagle K-1400 voltlohmlmil/iammeter in action. This has a A 
sensitivity of 20,000 ohmsfvolt d.c. and 5,000 ohms/volt a.c. 
•and measures d.c. voltage 0-SkV in 8 ranges at accuracy better 
than ±3% f.s.d., a.c. voltage a/so 0-5kV but in 6 ranges, d.c. 
current 0-10A in 6 ranges, a.c. current 0-10A in 4 ranges and 
resistance in three ranges, to 20MQ, Frequency response 
10Hz to 100kHz (for 2 5V, 10V and 50V a.c. ranges), and a 
dB scale is fitted. 



Fig. 5: An old favourite updated. The ► 
Avometer Model 8 MklV. Meter 
movement sensitivity 50 y. A full- 
scale, providing a sensitivity of 
20,000 ohmslvoft on d.c. and 2,000 
ohmsjvolt on a.c. Features include 
movement reverse control and over- 
load protection. A.C. voltage ac- 
curacy maintained up to 15kHz on 
250V range, suitable for audio 
frequency measurements. A dB scale 
is included. 

< 

Fig. 6: Heathkit Utility Solid-State 
Voltmeter, Model IM-17. This em- 
ploys 4 silicon transistors, 1 field 
effect transistor and 1 silicon diode 
and has 4 d.c, voltage ranges from 
1V to ikV (full-scale) and 4 a.c. 
voltage ranges from 12V to 1kV 
(full-scale). 







1035 




INSTRUMENTS 



(100mV) would be useful. Complementary ranges might 
than be 0-25V, 1V, 2-5V, 5V, 10V, 25V, 50V, 100V, 250V, 
500V, 1kV and, perhaps, 25kV, Remember that we often 
need to measure with fair accuracy down to 0-25V or less 
in transistor stages, so it is essential for the meter to 
feature well proportioned ranges down to at least 0-25V 
full-scale. 

D.C. current ranges are also important, but possibly 
marginally less so than voltage ranges. This is because 
when testing in printed circuit equipment we endeavour 
to calculate the current by measuring the voltage dropped 
across a known value resistor in the circuit carrying the 
current, simple Ohm's law then giving the answer without 
the need to break the circuit to introduce a current meter. 

Well proportioned voltage ranges are generally re- 
flected in the d.c. current ranges, from the lowest full-scale 
value allowed by the meter movement to several amperes 
without external shunts. For example, a 20,000 ohms/volt 
multimeter might have full-scale ranges of 50^A, 100^A, 
850/kA, 500/* A, 1mA, 2-5mA, 5mA, 10mA, 25mA, 50mA, 
100mA, 500mA, 1A and 10A. These, it will be noticed 
complement the voltage ranges Just mentioned. 

A.C. MEASUREMENTS 

A multimeter designed to measure a.c. voltage might 
not be equipped to measure a.c, current. There are two 
versions, the less costly one that measures a.c. voltage 
and the more costly one that measures a.c. current as 
well as voltage. In the valve days a.c. current measurements 
were more important than they are today, for valve heater 
current was an important parameter. 

It is still desirable to be able to measure a.c. voltage, 
however, for some audio equipment, in particular, is 
sensitive to main voltage. We also commonly need to 
know the a.c. voltage across the secondary windings of 
the mains transformer feeding the rectifier or the a.c. 
voltage applied, say, to the motor of a tape recorder or 
turntable unit. To some extent, depending on instrument 
design, we can also use the a.c. voltage ranges to measure 
audio signal provided the level is sufficiently high. This is 
said with some qualification, however, since the meter 
loading on the signal source and the frequency response 
shortcomings of the meter circuit can seriously affect the 
readout accuracy. 

A moving-coil movement responds correctly only to 
direct-current. This means that for a.c. measurements 
the instrument uses a rectifier, often of the bridge type. 
The nature of the ax. circuit reduces the instrument's 
sensitivity on the a.c. ranges, and it is not uncommon to 
find that the ax. sensitivity of a meter with a d.c. sensitivity 
of 20,000 ohms/volt is around the 2,000 ohms/volt mark. 
The a.c. volts ranges are thus generally fewer than the d.c. 
volts ranges, starting at about 1V full-scale instead of, 
perhaps, 100mV. 

A meter which also measures ax. current is similarly 
restricted, the first full-scale range being, perhaps, 1mA 
instead of 50^A or 100>A, as on d.c. 

Knowing the mains loading (e.g., W=VA) of a radio 
receiver or item of audio equipment—even if solid state- 



sometimes provides a clue as to a possible fault condition, 
and as this can be obtained only by measuring the ax. 
input current the meter can usefully possess at least a 
fairly high current range. 

The a.c. ranges are scaled in root mean square (r.m.s.) 
values based on siiewave input. Thus a signal which 
deviates from pure sinewave form will fail to provide an 
accurate r.m.s. indication. 



OTHER MULTIMETER 
MEASUREMENTS 

More advanced multimeters incorporate additional 
features which are sometimes useful for servicing applica- 
tions. For example, a decibel scale (or scales) can be used 
in conjunction with the a.c. voltage ranges to measure the 
power response, say, of an audio amplifier, provided that 
the frequency response of the meter is reasonably 'flat' 
over the audio spectrum and that the voltage ranges 
match the audio voltage across the load (W=E 2 /R). It is 
common for OdB to correspond to 1mW into 600 ohms, 
and the scale or scales may extend from — 1QdB to + 60dB 
or more. 

Some models also provide for the measurement of 
capacitance and inductance with an external adaptor (the 
Taylormeter, Model 38B, for example). 



MULTIMETER FEATURES 

More costly versions are equipped with either mechani- 
cal or electronic overload protection, which is certainly 
very useful in the service workshop! 

Another handy fitment is a switch for reversing the 
polarity of the test leads. Thus if the meter deflects against 
the stop, the switch can be operated to give a normal 
forward reading. 

Maximum readout accuracy is given by the models with 
large scales (Sin. or so), and to avoid reading error due 
to parallax effects, a section of the scale may carry a 
mirror (called anti-parallax mirror) so that the pointer can 
be aligned with its reflection when the reading is taken. 

Number of ranges, and facilities provided by a multi- 
meter, of course, reflect its price. The small 'pocket' 
instruments are useful for field activities, but for workshop 
applications a more valuable investment is desirable. 



ELECTRONIC MULTIMETER 

The electronic mUtirneter generally boasts features in 
advance of those already described. The high input 
impedance is a usefil attribute for certain tests, this some- 
times being around 11 M on d.c, and 1M or so on a.c. 

A.C. frequency response, too, is significantly enhanced, 
sometimes by an external diode probe. The Heathkit 
'Utility Solid-State Voltmeter', for example, has a ±1dB 
response from 10Hz to 1MHz. If the voltage sensitivity is 
in the order of millivolts full-scale, then such an instrument 
can almost be empbyed as an audio milli-voltmeter. The 
Avo Electronic Avoneter Type EA113 goes down to 10mV 
on its lowest range with an accuracy of ±1-25% from 
20Hz to 25kHz which makes it quite suitable for audio 
applications. The Grundig 'Universal Voltmeter', Model 
UV30 is another model suitable for audio work, in addition 
to the measurement of voltage and current, a.c. and d.c. 
This goes down to 100mV full-scale on the ax. range with 
an accuracy of —3% from 10Hz to 100kHz ±0-5dB. The 
instrument is battery powered and adopts field effect 
transistors. 



1036 




Fig. 7: Heathkit Audio Generator, 
Model AG-9U. Frequency range is 
from 10Hz to 100kHz with (ess than 
0-1% distortion from 20Hz to 10kHz. 
Output voltage is indicated on a 
4\in. meter with three scales of 
1 and 3 volts and —10 to +2dB. 



Fig. 9: The Heathktt (Heath, 
Gloucester Ltd.) Model I0-18U 
oscilloscope. This general purpose 
model has a Sin. tube, 4-5MHz 
bandwidth and 30mV (p-p)jcm. 
sensitivity. Sweep goes from 10Hz to 
500kHz. 



Fig .11 : A pocket-sized multimeter by 
Taylor, Model 127 A. This is suitable 
for bench and field work in industry 
and for the student and amateur 
radio enthusiast. Sensitivity is 20,000 
ohmslvolt d.c. and 1,000 ohmslvolt 
a,c. 





Fig. 8: An a.m. signal generator by Avo, Model HF133. The picture 
shows the facilities provided. 








Fig. 10 : A Universal Voltmeter by Grundig. A 
Model UV30. This uses field effect transistors, 
is battery powered and pocket size. Impedance 
as high as 30M and resistance measurement 
from m to 500MC1. 



Fig. 12: Grundig Oscilloscope Model 
TO 6\7. This is an example from the 
very wide range of test instruments 
by Grundig. Using solid-state de- 
vices, it is suitable for mains and 
battery powering, with facilities for 
powering from external vehicle 
battery. Y bandwidth 0-6MHz -3dB 
and sensitivity 30mVfcm. 





INSTRUMENTS 



For checking the gain of r.f. and i.f. stages one needs 
to measure r.f. and i.f. input and output signals, and this 
mode of measurement is sometimes catered for by a 
diode probe designed for use with an electronic multi- 
meter or similar instrument. Signals up to 100MHz (some- 
times higher) can be measured by this method. 



AUDIO MILLIVOLTMETER 

This instrument differs from the multirange electronic 
meter in that it is designed to measure a.c. voltage only 
from low audio-frequency up to 30kHz or more. Some 
models, in fact, measure up to 1MHz or beyond this into 
the video-frequency spectrum. 

Design is based on high response accuracy over the 
intended frequency range and also very high sensitivity 
on the low ranges. Indeed, some ultra-sensitive models 
give full-scale deflection from a signal as low as 100/^V 
(sometimes less!). With such sensitivity it is possible to 
measure very low-level audio signals, such as those 
delivered by a magnetic pickup cartridge or microphone. 

A multiplicity of ranges, based on a calibrated input 
attenuator, often extends the full-scale readout to several 
volts or tens of volts. Readings are commonly scaled in 
r.m.s. values, though there may also be peak voltage 
scales or a switch or control to change the readout from 
r.m.s. to peak. 

As this sort of instrument is designed for audio and 
video applications it is almost certain to feature a decibel 
scale. The moving-coil meter is operated from rectified 
signal obtained from the output of an amplifier, the various 
ranges being catered for by switched attenuators. 

Mains and battery powered versions are available and 
quite a few models are equipped with an amplifier output 
socket, prior to the meter rectifier, so that the measured 
signal can be viewed on the screen of an oscilloscope. 
This is useful when the instrument is reading audio 
distortion via a distortion analyser, for the 'scope display 
then reveals the nature of the harmonics of which the 
distortion is composed. Battery-powering leads to port- 
ability and reduces hum-loop problems when tests are 
being made in low-level circuits. 



DIGITAL READOUT 

Although digital instruments are fast becoming popular 
in laboratories, it will be some time before we can afford 
them specifically for servicing and experimental applica- 
tions. At the time of writing a digital multimeter costs 
about three times more than an equivalent analogue 
instrument. 

For lab. work the appeal ties in the accuracy, ease of 
readout and high sensitivity. For example, the Digital 
Avometer, Model DA112 features voltage ranges from 
10O/*V to 1-5kV (with a 50% over-range facility) at an 
accuracy to 0-1 %. Readout is from a 3£ digit display with 
automatic decimal pointing, and the design covers both 
mains and battery powering. 

Cost lies essentially In circuit complexity, but with the 



advancement of integrated circuits (of which many already 
employ) and mass demand, the cost is almost certain to 
decline eventually, tiough this may not be in the very 
near future! 



SIGNAL GENERATORS 

For radio servicing the signal generator must yield a 
modulated carrier-wave and operate over the bands 
corresponding to those tuned by the receiver. Modulation, 
too, must match the design of the receiver. Thus a.m. 
receivers require amplitude-modulation and f.m. ones 
frequency-modulation. The generator should also tune 
over the i.f. spectrurr, commonly 107MHz f.m. and 470kHz 
a.m. 

An important part of the design is the output attenuator. 
This should be reasonably accurate so that a fair approxi- 
mation of the strength of the signal fed to the receiver is 
known. This is necessary for determining the sensitivity 
of the receiver. Calibration is either in decibels below the 
maximum signal output (sometimes referred to OdB) or 
direct in juV and mV. A switched attenuator generally sets 
the output range, which is then controlled by a 'fine' 
attenuator. 

Some models have; facilities for varying the modulation 
depth and a meter fcr setting the signal level prior to the 
attenuator, but for general servicing applications such 
refinements are not essential. 

For range extension harmonic working is sometimes 
adopted. This is not generally a desirable scheme, al- 
though it tends to reduce cost. Fundamental working even 
into the higher frequency bands makes life less complica- 
ted and reduces errors which can sometimes result from 
harmonic working. 

Models designed for radio and television servicing 
commonly incorporate a fixed-frequency audio oscillator, 
at 400Hz or 1kHz, for modulating the carrier-wave, and the 
signal from this is often brought out to a front socket, 
either at 'full force" or via a variable attenuator. This signal 
is useful for making tests in audio sections of receivers 
and in amplifiers. Modulation depth is fixed at approxi- 
mately 30%, though it can vary slightly over the frequency 
ranges. 

Even though the irstrument might produce only ampli- 
tude-modulation, pro/ided the modulation can be switched 
off and the r.f. range embraces Band II (from about 87 to 
108 MHz), it can be ussed for f.m. receiver servicing to some 
extent (this will be explained in the forthcoming series). 
F.M, generators are usually more costly than a.m. counter- 
parts, but models are made which switch over a.m. and 
f.m., covering the range from about 130kHz to 250MHz over 
various bands. 

For the visual alignment of radio receivers (using an 
oscilloscope to display the response characteristic), a 
special kind of signal generator is required, commonly 
referred to as a 'wobbulator*. The r.f. output from this 
swings either side of the nominal carrier frequency in 
synchronism with tie X sweep of the oscilloscope, 
sufficient to embrace the full width of the response. A 
reponse display is then obtained by feeding the detector 
output of the receiver to the oscilloscope Y input. 



AUDIO GENERATOR 

For audio testing the generator should tune from at 
least 20Hz to 20kHz; but many go above this frequency. 
Signal output is a sinewave, but many instruments can be 
switched to change the sinewave to a square-wave, 



idy 





Fig. 13: For more advanced measurements and tests, this 
Universal Bridge by Avo, Model B.150, caters for a wide range 
of inductance, capacitance and resistance measurements'. 
Balanced null point is indicated by a meter, while the value of 
the component under test is automatically presented in digital 
form. 



Fig. 14; Avo Transistor Test Set, Model TT.166. Design is for 
the measurement of bipolar transistor d.c. parameters. Tests 
can be made at very low collector currents appropriate to 
modern devices (1fj.A to 1mA), p-n-p and n-p-n. Operation is 
from two internal 9V batteries. 





Fig. 16: The still popular Taylor Model 68 AIM signal generator. 
Frequency range is from 100kHz to 240MHz (all on funda- 
mentals) over 8 ranges. Although a.m. only, the instrument is 
suitable for the alignment of ratio detectors and f.m, r.f. and i.f. 
stages. A variable 400H2 audio output is avaiiable and an r.f. 
monitoring meter allows accurate setting of the signal applied 
to the attenuators w 



Fig. 15: Interesting Signal Tracer, Model SV2, by 
Grundig. Using transistors, the instrument is battery 
powered and of handy size, Signal is traced via a test 
prod which, after amplification, is indicated by meter 
or loudspeaker. 



■^ Fig. 17 : Grundig Grid Dip Resonance 
Meter, Model TR300. This model 
covers 0-95MHz to 300MHz in 8 ran- 
ges (Model TR30 95kHz to 30MHz) 
and is battery powered. A very useful 
instrument for experimenters since 
not only is the frequency of an 
external tuned circuit indicated by a 
change in current, but switching 
changes the mode to absorption 
wavemeter and receiver, operated 
through a headphone set. 



Fig. 18 : Taylor Valve Tester, Model ► 
45D. This general purpose instrument 
is capable of testing almost all 
thermionic valves with the exception 
of the larger transmitting type. There 
are ten valve bases, including the 
more recent B10B and B9D, and a 
special B14E base accepts a range of 
plug-in adaptors available; to cover 
new and old valves. Mutual con- 
ductance is measured (emission of 
diodes), and there is also a "replace 
— ? — good" scale for speedy 
appraisal. 




1039 




INSTRUMENTS 



useful for 'transient' testing audio amplifiers. 

The sinewave must be as pure as possible, especially 
when the signal is to be used for distortion measurements, 
and for this application the total harmonic distortion on 
the signal should be significantly less than 1%, However, 
it is possible to 'filter" the signal from a generator of 
relatively high distortion to delete the harmonics, thereby 
making it more suitable for thud, measurements (this, too, 
will be explained in the forthcoming series). 

Maximum output should be a volt ortwofr.m.s,), and the 
attenuator should reduce this i it decrements of 20dB, with 
a 'fine' attenuator varying the 'set output' down to zero. 
It Is also important for the audio signal output to remain 
substantially constant over the entire frequency range. 

OSCILLOSCOPE 

For many radio and audio applications an oscilloscope 
with a Y bandwidth up to 3MHz can be very useful. Cost 
can be cut by building one's own from a kit of parts, such 
as the excellent Heathkits. The General Purpose Service 
Oscilloscope, Model OS-2 is a good illustration. This, by 
Heathkit, sells at £29-20 (carriage 60np) as a kit and for 
£44-20 (same carriage) in ready-to-use form. 

For more specialised circuit investigations, however, 
a Y bandwidth to — 3dB points) up to 10MHz and beyond 
is demanded; this applies to the study of very fast pulse 
signals and transients, etc. 

X bandwidth is less critical for most normal applications 
(that of the Heathkit being 2Hz to 300kHz ±3dB, and the 
Y bandwidth 2Hz to 3MHz ±3dB). Y sensitivity (e.g., 
vertical deflection of the spot) is also important, and this 
should be at least 250m V p-p per cm. A useful feature is 
a 'voltage calibrator' which switches an a.c. voltage of 
known amplitude to the Y input. 

For use with a wobbulator an X (timebase) output 
terminal should be available, this then being coupled to 
the X or sweep input of the wobbulator for securing a 
response display as already mentioned. 

X sweeps should match the Y bandwidth in terms of 
waveform time. These are sometimes given as time (/<S, 
mS or S) per cm. of horizontal sweep. 

It is also useful to be able to switch off the timebase so 
that external signals can then be applied to both the Y 
and X amplifiers. Certain tests of phasing require the use 
of these two circuits without the Influence of the timebase. 
The display is locked on the screen by a synchronising 
signal from the source, and most recent 'scopes embody 
an automatic circuit forthis, the sync signal being extracted 
internally from the test signal. 

Most instruments designed for general servicing still 
run on valves, particularly the less costly ones, but there 
is a trend towards the use of solid-state devices, giving 
a choice of mains or battery powering and the bonus of 
portability. 

Screen diameter is not all that important for radio and 
audio servicing, though obviously the larger, the better; 
but some sort of calibration is desirable, and this com- 
monly takes the form of a graticule scribed in cm. squares. 
Another useful feature is X expansion. This merely 

1040 



consists of an amplifier through which the timebase 
signal passes to the X plates of the cathode-ray tube. 
With the X expansion control— a variable attenuator — 
fully clockwise horizontal deflection just fills the screen. 
As the control is ad/anced so the deflection increases. 
It is thus possible to expand a waveform display hori- 
zontally (as well as vertically by the Y attenuator) to allow 
otherwise hidden artifacts to be examined. Turning on X 
expansion is tantamount to increasing the timebase sweep 
velocity, so the expansion control complements the 
sweep control. 

ft is sometimes required to examine two signals simul- 
taneously and to compare one with the other. For this a 
dual beam 'scope is reeded, with duplicated Y amplifiers, 
etc. Such instruments cost more than the single beam 
variety and are found mostly in laboratories. However, it 
is possible to secure two displays from a single beam 
model electronically, using a special switch. A good 
example is the Heathkit Electronic Switch, Model S-3U, 
which costs £1630 as a kit or £28-30 in ready-to-use form. 

i 

DISTORTION ANALYSER 

For audio amplifier servicing of a serious nature an 
important instrument is the distortion analyser. Basically, 
this consists of a tunable notch filter through which a 
sinewave signal after passing through the amplifier is fed 
to a sensitive audio millivoltmeter. The sinewave signal 
fed to the input of the amplifier under test is obtained from 
a low distortion audio generator, and the idea is that the 
'notch' deletes the fundamental leaving only the harmonics. 
These are measure by the audio millivoltmeter and their 
total voltage is then compared with that of the sinewave 
signal proper across the same output load in terms of 
percentage total harmonic distortion. 

A laboratory instrument at reasonable cost— Model 
Si452— is made by J. E. Sugden &. Co. Ltd. of Cleckheafon, 
Yorkshire. When complemented with a millivoltmeter and 
generator t.h.d. readouts to less than 0-1% are possible. 

Integrated instruments (e.g., embodying the audio 
generator and readout) are also available. These are 
generally very costly instruments, but for less exacting 
work inexpensive Heathkit models are available, one for 
t.h.d. measurement (Model M-58U) and another for Inter- 
modulation distortion analysis (Model IM-48), 

It is obviously impossible to survey the whole field of 
servicing test instruments in a supplement of limited 
space, but it is hoped that the foregoing, and the accom- 
panying illustrations, will give a fair impression of the 
type of instruments currently on offer. 



New Servicing 
Series 

starts next month in 
PRACTICAL WIRELESS 

An introduction to fault-finding theory and 
practice in radio and Hi-Fi equipment. 



CfoU&n/Ht 



INSTRUMENTS 



A range of micro soldering instruments 
combining high performance with really 
small dimensions and providing 
exceptional versatility. 



Weighing about \ oz. (less flex) these 
miniature tools ensure the utmost 
accuracy and safety in use, resulting in 
consistently high standards of soldering 
with minimum operator fatigue. 



Ultra-slim unbreakable nylon handles 
give a cool, comfortable grip for 
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Slip-on bits are fitted over the element 
shaft, so absorbing all the heat 
produced and giving high performance 
with rapid heating and recovery. A wide 
range of interchangeable tip sizes is 
available to suit different types of work. 



There are ADAMIN models 
from, 8 to 24 watts, in vbltages 
from 6v. to 240v. 



Please ask for New Leaflets 10/1005/7. 

LIGHT SOLDERING 
DEVELOPMENTS LTD. 

28 Sydenham Road, Croydon, CR9 2LL 
Telephone 01-688 8589 and 4559 





I'D RATHER 
HAVE A 

MINITEST" 

The SEI MINITEST has made a remarkable impact in the 

pocket-sized multi- range meter market, fay making itself 

a firm favourite with discerning people in the industry. 

Let's look into the reasons why. 

First the appearance. Diminutive, neat, wipe-clean 

cycolac case with shock and magnetic ,ield proof steel 

liner. Controls are simple and easy to use. 

Second, the range. The Minitest 

measures a.c. and d.c. voltages d.c, 

current and resistance over 20 ranges 

to a sensitivity of 20,000 and 2,000 

ohms p"sr 'olt d.c. and a.c, respectively. 

Third, high voltage probes. These 

extend the range to 25 or 30kV d.c. 

Little wonder the Minitest is preferred! 



SALFORD ELECTRICAL 

INSTRUMENTS LTD 

Peel Works. Barton Lane, Eccles. 

Manchester M30 0HL 

Telephone 061 -789 5081 *••« 66 m 

A Member Company of GEC Electrical 

Components Ltd. 






(mWF) ( jac) 




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PL4001 50 lOp flp 8p 7p 6p 

PL4002 100 lip lOp 9p 8p 7p 

PL4003 200 12p lip lOp 9p 8p 

PT40D-i 400 13p lip lOp 9p 8p 

PL4005 600 ISp 18p lip lOp flp 

PL4006 800 17p 16p 13p ISp lOp 

PL 400 7 1000 20p 17p ISp 13p lip 

3 AMP PLASTIC WIRE ESDED RECTIFIERS 



Tvpe P.I.V. 
PL7001 50 
PL70O2 100 
PL7003 200 
PL7004 4O0 
PL70O5 600 
PL7006 800 
PL7007 1000 



H9 50+ 100+ 500+10004 

SOp ISp 17p ISp 14p 

ISp 17p 

19p ISp 

Sip 20p 
S3p 

21;- 



19p 
SOp 
SSp 
24p 
25p 
SSp 



SSp 

S4p 



ISp 
10;i 
Of 

20[, 
21 u 
82p 



HEEUTBRE POTTED BRIDGE 
(SILICOH) SIZE Hit 



Cu 

Type P.I.V. rent 

602 50 2 amps 

1002 100 2 ampa 

2002 200 2 amps 

4002 400 2 amps 

504 50 4 amps 

1004 100 4 amps 

2004 200 4 amps 

4004 400 4 amps 

1006 100 B amps 

2006 200 6 amps 

4006 400 fi ampi 



RECTIFIERS 
tins. 



1-49 50-L 
SSp 50p 



eop 

70p 
8 Op 
OOp 
70p 
75p 
SOp 
75p 
SOp 



SBp 
BSp 
75p 
SSp 
60p 
70p 
75p 
70p 
75p 



100+ BOO 
4Bp 4 Op 



SOp 

eop 



4Sp 

55p 



70p esp 

SOp 45p 

SSp SOp 

ssp eop 

70p 65p 

SSp SOp 

7 Op SSp 

SOp SOp 



MFC4000P 

1.C.10 

PA246 

TAA283 

TAD100 

TADIIO 

MC1303 

UL900 

UL914 

UL923 

LA709C 

IROM4 



ilolomla 

Sinclair 

6 Watt 

llullard 

Mullard 

Mullard 

Motorola 

Fairchild 

Fairchild 

Fairchild 

Fairchild 

Motorola 



aia 

E275 

£2-45 

76p 

£197 

£197 

ES-60 

40p 

40p 

60p 

75p 

£2-75 



2ENER DIODES 
400 M/W 6% 
Miniature 
BZY 88 Range 
All voltages 3.3 
Volt-33 Volt. 
ISp t:aeli. 

25+ ISp 

100+ lOp 

300 + flp 

1000+ Sp 

Any one type. 

ZEJFER DIODES 
3 Walt Plastic 
Wire Ends 5% 
All voltages 6.8 
-100 Volts. SOp 
each. 

85 + 27p 

100+ SSp 

500+ SSp 

1000+ Sip 

Any one type. 



ZEJTER DIODES 
1 Watt 5% 
Plastic Win ! Ends 
6.8 Volt all volt- 
ages to 100 Volts 
SSp each. 

35+ 20p 

100+ ISp 

S00+ 16p 

1000+ ISp 

Any one tjpe. 



ZEMER BIDDES 
7 Watt Stufl 
Mounting 5% 
AB voltage; 
100 Volts, 
each* 

25+ 

100+ 



40p 



AQy one type. 



SSp 
30p 



POWER RECTIFIERS 

SILICON RECTIFIERS 

STUD MOUNTING 6 AMP RAS3E 

P.I.V, 1-49 50+ ]0OJ- 

BVZIO 800 40p SSp 3up 

BYZU 600 SSp SOp SSp 

BYZ12 400 30p SSp 20p 

BYZ13 200 SSp 20p 17p 

10AMP RECTIFIERS 

P.I.V. 1-49 50 



9K10S 
SK20S 
8K403 
SK88B 

SK«n:s 



100 
200 
400 
BOO 
SOO 



4Sp 
SOp 
SSp 
SOp 

75p 



100- 
40p 37p 



4Sp 
50p 
SSp 
70p 



42p 
45p 

SOd 
65p 



SEMI-CONDUCTORS 

| i.OOK AT THESE PRICES FOR 
QUANTITIES FROM STOCK 



AFI 14 Mullard 25p 
2S + 20p 
100 + I7p 
500 + I5p 



AFII6Mu lardlSp 
2S + 20p 
100 + |7p 
SCO + ISp 



2N3055 75p 

Mullard I I5watt 

Silicon Power 

25 + SSp 

100 + SSp 



BFY90 65p 

1000 MC/S 
25 + 60p 
100 + SSp 
500 + SOp 



AFI 39 30 p 

Siemens V.H.F. 
25 + asp 
100 + 22p 
500 + |9p 



OCI 70 Mullard 25 p 
25 + 2lp 
I0O + I7p 
500 + ISp 



OCI7I Muilard 30p 
25 + 27p 
100 + 22p 



BY 1 27 Muliard 20p 

lOOOv I amp PI as*, it 

25 + I7p 

100 + ISp 

500 + I 3p 



BCII3 SG5 25p 
25 + 20p 
100 + I7p 
SOO + ISp 



AFI IS Mullard 25p 
25 + 20p 
100 + I7p 
500 + ISp 



AFII7 Mullard 25p 
25 + 20p 
100 + I7p 
500 + I5p 



2H38l9Texas35p 

25 + 30p 
100 + 25 p 
500 + 23p 

1000 + 20 p 



2N2646 SOp 

Motorola 
Unijunction 

aS + 44p 
100 + J7p 
500 + 33 p 



AFI 86 40 p 

Mullard V.H.F. 

25 + 35p 

IOC + 30p 

500 + 2Sp 



BYZI3 25 p 

Mullard 6a 200v 

25 + 20p 

100 + I7p 

500 + ISp 



BCI07, BCI08. 

BCI09 I2p each 

I.T.T. Plana rs 

25 + lip 

100 + lOp 

50O + Sp 



OCP7I 97p 

Mullard Photo 
25 + 85p 
100 + SOp 
500 + 75p 



OA202 I Dp 

SILICON Diodes 
25 + Sp 
100 + 6p 
500 + 5p 

1000 + 4p 



0C42 Mullard 30p 

25 + 2Sp 

100 + 21p 

500 + 21 p 

1000 + ISp 



OC45 Mullard 

25 + 13p 

100 + IZp 

500 + I Op 

1000 + Sp 



5p 



OC75 Mullard 2Sp 
25 + 2lp 

100 + I7p 

500 + I5p 
1000 + I3p 



OOO 97p 

Mullard lOOv 
25 + SSp 
100 + SOp 
500 + 75p 



0C28 62o 

Muliard Power 
25 + SSp 
1 00 + SOp 
500 + 42p 



OC7I Mullard 
25 + I2p 
100 + I Op 
500 + 8p 



Sp 



ORPI2 Mullard SOp 

25 + 45p 
100 + 42p 
500 + 40p 



2N930 25p 

25 + 23p 
100 + 20p 
500 + I7p 
1000 + ISp 



0C72 Mullard 2Sp 

25 + 20p 

100 + J7p 

SOO + ISp 

1000 + I3p 



0C44 Mullard I7p 

25 + I5p 

100 + I3p 

500 + lip 

1000 + lOp 



OCI 39 Mullard 2Sp 
25 + 20p 
100 + I7p 
500 + I5p 



OC8I Mullard 25 p 

25 + 20p 

100 + 17p 

500 + I5p 



OC83 2Sp 

25 + 20p 

100 + I7p 

SOO + ISp 

1000 + I3p 



0C84 



25c 



25 + 20p 

I0O + I7p 

500 + I5p 

1000 + lip 



AF239 42p 

2S + 35p 

100 + lOp 
500 + 25p 
1000 + 20p 



SEMI-CONDUCTOR DEPARTMENT 

303 EDGWARE RO.. LONDON, W2. TEL: 01-723 100B/9 

CALLERS 356 EDGWARE ROAD W2. 



NEW LIST NEW PRICES DISCOUNTS 

1971 TRANSISTOR 10% 12 ANYONE 

LIST 1000 - 15% 25 TYPE 

SEND f OH YOUR FHEE POSTAGE 7p. 

COPYTOBAY... ALL ORDERS 



1042 




ALL IN THE 
MAY ISSUE, ON 
SALE APRIL 8th 



STATION FOCUS' SIX 



At best the performance of the average 
superhet receiver depends largely upon the 
proper alignment of the various tuned circuits. 
In this 'no-compromise' medium and long 
wave receiver, the "Station Focus" Six, 
separate panel controls are included for the 
correct alignment of the critical circuits. 

The prototype has been buijt on a clear 
perspex panel, as shown on the right, and the 
photographs included in the article will greatly 
assist the construction and later checking of 
the circuit 

An attractive but simple wooden cabinet 
completes the receiver which, because of its 
simplicity is ideal for the beginner but because 
of its performance is also suited to the more 
advanced constructor. 




NEW SERIES... | hi-fi 

SERVICING SIGNAL GENERATOR 

AN INTRODUCTION TO FAULT-FINDING 

There aren't many members of the electronic fraternity 
who haven't dabbled in servicing — even if it's only to 
change the battery or clean the earphone socket connec- 
tions on a friend's radio. 

This new series, starting from scratch takes the reader 
right through from basic principles to the more advanced 
aspects such as alignment of f.m, superhets and fault- 
finding on Hi-Fi systems. 

It is written by G. J. King and H. W. Hellyer. authors of 
previous popular series on servicing. Be certain not to 
miss the start of this new series. 



■ 




AUDIO FANS ARE NOT FORGOTTEN IN THE 
NEXT ISSUE AND A 10W TRANSISTORISED 
AMPLIFIER INCLUDING PREAMP. IS DES- 
CRIBED. 

MANY OTHER ARTICLES INCLUDE THE 
POPULAR "TAKE 20" AND "I.C. OF THE 
MONTH" SERIES. 

BE SURE NOT TO MISS THE MAY ISSUE- 
ON SALE APRIL 8th. PRICE 20p. 



The high standards of modern audio amplifiers have made 
many older audio signal generators obsolete; it is obviously 
a waste of time trying to trace 0.1% distortion if the inherent 
distortion of the source is comparable. 

Confidence in test gear is important and for this reason, 
starting in the May issue, the circuit and complete building 
instructions are given for a laboratory quality signal 
generator. Distortion at 1kHz is a mere 0,01% and output 
ranges run from 15Hz to 150kHz ± IdB though an additional 
range goes up to 1.5MHz. 

Output can be up to 12V peak-to-peak and either sine 
or square wave outputs can be selected. 



1043 



I 





pinr 

sound effects 

SYNTHESISER 



PART 2 



THE general layout of the complete unit and the circuits for castanets, 
cymbal and snare drum were dealt with in Part I. With the excep- 
tion of the Bell Chime circuit, all the others can be constructed and 
operated individually as each has a fairly large signal output. If all the 
generators are to be used together i.e., as in the original unit, they must 
be finally connected together via a mixing output pre-amplifier which will 
be dealt with later. 

The next circuits include the Triangle No. 4, Wood Block No. 5, Taxi 
horn No. 6, Train Whistle No. 7 and Bell Chime No. 8 and each is 
assembled on an s.r.b.p. board as those in part 1. As will be seen from the 
board layout diagrams given in this article, some boards are pretty full 
with components. For this reason the components used should be as 
physically small as possible. 

Circuit for Triangle — No. 4 

The sound of a triangle is clear and high pitched and the waveform 
almost sinusoidal. The circuit as in Fig. 11 therefore, employs a phase 
shift oscillator adjusted for a frequency of approximately 4500Hz. The 
output from the oscillator Trl is first attenuated via R21 and then taken 
to the control amplifier Tr3. This amplifier is triggered by Tr2 which 
generates a control voltage waveform as shown in the Triangle Circuit 
waveform B Fig. 21. When the key No. 4 is closed a pulse (Triangle Cir- 
cuit waveform A) is generated which causes Tr2 to conduct. This brings 
the emitter of Tr2 almost up to the supply voltage and C9 becomes 
charged. Tr3 takes it's h.t. from C9 which then slowly discharges and 
produces the required decay effect. The sine-wave output from Trl, 
although considerably attenuated, does slightly overdrive Tr3 and this 
helps to provide the characteristic metallic sound of a triangle. Note that 
the key click filter C7/R9 must be included. The resistor R14 in series 
with C9 reduces the otherwise very hard attack and C9 itself determines 
the decay time. If C9 is made larger the decay time will be larger and vice 
versa. The pitch should he adjusted as close as possible to 4500Hz and 
this can be done by either reducing the value of Rl slightly or by con- 
necting another resistor in parallel as R1A. The circuit board layout is 
shown in Fig. 12. 

Circuit for Wood Block— No. 5 

This is a little less complicated than the other circuits and employs only 
two transistors. The circuit is shown in Fig. 13 and in this Trl is a phase 
shift oscillator biased to cut off and is turned on only when Tr2 conducts 
i.e., when the key (No. 5) is closed. The pitch and decay time are both 
very important if a realistic sound is to be produced. For instance, if the 



•-HT+22-24V 




»-HT- 



Fig. 11 : The circuit of the triangle sound synthesiser. 



decay time is too long the sound 
will be too much like a bell and 
if too short will sound like a 
click. Some adjustment of R9 
may be necessary to achieve the 
right period of decay. Pitch can 
be altered by slight variation of 
Rl which is nominally 8-2k£l. 
Adjustment of both decay time 
and pitch rather depends on 
aural estimation of the sound. 
The strike and decay control 
voltage and output waveforms 
are shown in Fig. 21. (Wood- 
block Circuit waveforms A and 
B respectively.) The circuit board 
layout is shown in Fig. 14. 

Circuit for Taxi 
Horn — No. 6 

This is another of the more 
complex circuits and employs 
four transistors as shown in Fig. 
15. First however, note that the 
signal from the multi -vibrator 




Screened 
lead 



Fig, 12; The component layout 
of the triangle circuit. 




W. *R1 Pilch (See text) * R9 Decay time (See text) 
Fig. 13: The wood block sound circuit. 



An internal view of the completed project. The board shown is for 
the castanets circuit. 



1045 



Trl-Tr2 is also used for the bell 
chime circuit No. 8. IF the taxi 
horn circuit is to be used by it- -*- 
self the lead out to R16 on the r],{ 
bell chime circuit will not be 
necessary. The signal from Trl- 
Tr2 is a typical multi-vib. wave- 
form which is modified and at- 
tenuated by the network R6, R7, 
C5 and R12. The pitch should be 
adjusted to between 200 and 
250Hz by slight variation of R2 
and the attack/decay charac- 
teristic by RI5 and R16. Depres- 
sion and instant release of the 
key No. 6 should produce a 
short but typical 'honk' sound 
characteristic of old bulb type 
car horns. If the key is depressed 



Key N°5 




HT- 



14: The component layout of the 
wood block synthesiser. 



To R16, N°8 Chime circuit 



•R20 
' 10k 




■HT+2Z-Z4V 



Output to 
CIO mixer amp 




en 

6B00p 



$• H2 Pitch {See text) 



* R151 

* R16 



Attack /Decay (See text) 



Fig. 15: The taxi horn sound synthesiser circuit, The various waveforms produced are shown in Fig. 21. 



and held down the decay will be 
very slightly longer but the 
sound will die away completely. 
The circuit is triggered by Tr3 
and the function of this transis- 
tor and it's triggering voltages 
are the same as those (except 
for the decay time) for the tri- 
angle and cymbal circuits. The 
triggering voltage waveforms 
are shown in Fig. 21 (Taxi Horn 
Circuit waveforms A, R and C). 
The circuit board layout is 
shown in Fig. 16. 

Circuit for Train Whistle- 
No. 7 

Two transistors and a noise 
diode type Z1J are required for 
this circuit as shown in Fig. 17 
and which produces a typical 
steam train whistle complete 
with noise content and pitch 

1046 



1 To R16 N°8 Chime circuit 



Fig. 16 : The component layout of the b\xi horn sound synthesiser. 




■ 



-co 



^ HH 




HT+ 22-24 



BOOOp 



R1 
12k 

§ 



'R2 
;i2k 



i^MM^ 



1 — ' <: HU ^^ 

is (l w 



I R1 Pitch (See text) 



NDI 
ZU 



R9 
220k 

ce 



0*03 



■RIO 
■68k 



R21 

■AMr 

39 k 



— + T * 

T10 Di 
— *4 

OAST 



R13. 
12k- 



■R22 
■ 15k 



R12 

;izok 




si 

L£ | 



■R15 
'10k 



Tr2 

BC108 



£ 



R16 
47k 



I CIO 
10-2 



R14 
4-7k 



C11 

* 

0-2 



R20; 
220k. 



Fig. 17: The circuit used for simulating the train whistle sound. 




Output to 

mixer amp 

R7 



Screened 
lead 



Key NO? 



■H7- 



variation. The transistor Trl is 
a phase shift oscillator, the out- 
put of which is attenuated via Mounted 
R9. The pitch should be approxi- at end of 
mately 1000Hz and adjustment ' 
to attain this can be made by 
slight variation of El. The noise 
generator NDI is the same as 
used for the cymbal and snare 
drum circuits and it's output is 
slightly attenuated by Rll. The 
transistor Tr2 takes the signal 
from Trl and NDI simul- 
taneously but is normally biased 
to cut off by R14/R16. When key 
No. 7 is depressed Tr2 conducts ht— 
and passes the combined sine- 
wave and noise signals. How- 
ever the signal output from Tr2 
is also directed via C10 to the 
diode rectifier circuit R22, Dl Fig. IB: The component layout for the circuit in Fig. 17, the train whistle synthesiser. 




-vw 




t 



Key N°8 



Cl 
100 



C5 
0-2 



:220k 



-»-HT+22-2W 



$ R1 Pitch (See text) 




R 12, 120 k 
-AAA 




To Taxi horn circuit R6/C6 



Fig. 19: The bell chime synthesiser. The waveforms of the various stages are shown in Fig. 21. 



1047 






and CI 3. The negative voltage 
derived from this via R21 is 
applied to the base of Trl and 
produces a slight change in the 
pitch of the whistle frequency a 
fraction of a second after its 
initial sound. It is however, im- 
portant that the white noise con- 
tent of the whistle is not too 
great. The effect, which is that of C1 
hissing steam, should be only 
just apparent and should appear 
on the output waveform as 
shown in Fig. 21. (Train Whistle 
waveform B.) The output wave- 
form should also appear slightly ^_ 
clipped at the top. Adjustment to H1 ~ 
the level of the white noise con- 
tent can be made by altering the 
value of Rl slightly i.e., increase 




To Taxi horn 
circuit R6/C4 



Fig. 20: The component layout of 
the belt chime circuit. 




The various boards are shown at the centre and right, the power supply 
on the left. 



Rll for a decrease in noise content and vice versa. 
The circuit board layout is given in Fig. 18. 



Bell Chime Circuit— No. 8 

A deep hell chime, similar' to that produced by 
a large clock for instance, is a complex sound made 
up of an undulating fundamental and many over- 
tones. To achieve a close approximation of this with- 
out having to resort to the use of filters and/or a 
number of tone generators, a multivibrator has been 
used for the fundamental pitch and overtones. A 
strong heating or undulating effect is produced by 
adding another signal at almost the same frequency 
as the fundamental. This extra signal is obtained 
from the taxi horn oscillator. The harmonics of 
this also add considerably to those produced by 
the bell chime oscillator and the result, after suit- 
able attentuation and 'voicing,' is a deep undulat- 
ing but strident clock chime. The triggering circuit 
for the bell chime is produced by Tr3 which is 
switched on by key No. 8. The action of the circuit 
is the same as that used for the cymbal and triangle 
circuits and the decay time about the same i.e., two 
to three seconds. The output from the bell chime 
oscillator Trl-Tr2 is voiced by R6/C5 and attenuated 

1048 



Junction C8-D1 Junction R14-C9 Output al C11-R19 



2-3secs— \ 
Triangle circuit 



I— 2-3secs—j 



Junction C7-D1 Junction R15-C8 Output C1D-C11 




— 1/ — U^-J " 

'"^appron 
Taxi horn circuit 

Junction C6-D1 Jun;tion R14-C7 Output R20-R21 



200-300 
mV pk 



Bel! chime circuit 



Junction R7-R9-C4 Output C5-R11 




Wood block circuit 



Junction C6-R9 Output R20-R19 

(b) f~"A"A71" * f\ "ftfi ~ 

u 10V pkj 1 II II r 20D-300J I I 1 1 Li L 

approx 1 J 1 / II mV pk 

I ' la) " ~ (b)~ 

" 'tz 1000 Hz plus 

..ave noise signal 

Train whistle circuit 



Fig. 21 : The waveforms produced by the circuits described in Part 2. 
If possible these .ihou/d be checked on an oscilloscope. 



by R12. The signal from the taxi horn oscillator is 
treated in much the same way by R16, C8 and R15. 
Both signals are fed to the base of Tr4. Further 
attenuation and voicing is introduced at the output 
from Tr4. The frequency of the signal produced by 
Trl and Tr2 should be adjusted by slight variation 
of Rl so that a slow audible beating effect is obtained 
when the sound is keyed. Do not alter the pitch of 



I 



* components list-part two 



Triangle Circuit No. 4 



Transistors 

Tr1, Tr2, Tr3 

Diodes 

D1, D2 

Resistors 
R1 12kil 
R1A 18kft 

R2 12kQ 



BC108 Mullard 
OA5 Mullard 



R3 
R4 
R5 
R6 
R7 



12kQ 

120k-Q 

2-2k£2 

10kQ 

3-3kQ 



R8 10kD 

R9 560Q 

R10 470kQ 

R11 47kO 

R12 10kQ 

R13 1Mfi 

R14 820-Q 



R15 12kO 

R16 120k£} 

R17 1Qkfi 

R18 2-2kfl 

R19 18kO 

R20 1-5kQ 

R21 220kQ 



All *W, 10% tolerance 



Capacitors 
C1 250«F 



C2 
C3 
C4 
C5 



1000pF 
1000pF 
1000pF 
10/^F 



C6 390 pF 



C7 0-1/<F 

C8 1 -SftF 

C9 25// F 

C10 10//F 

C11 500pF 



Circuit for Woodblock No. 3 

Transistors 

Tr1, Tr2 BC108 Mullard 



Resist 


ors 






R1 


8 2kil 


R6 


470kQ 


R2 


12kQ 


R7 


680k<> 


R3 


iookn 


R8 


39kn 


R4 


Ikft 


R9 


120kH 


R5 


10kQ 


RIO 


10kfi 



All }W, t0% tolerance 

Capacitors 

C1 2200pF C4 0-1/tF 

■ C2 2200pF C5 390pF 

C3 2200pF 

Circuit for Taxi Horn No. 6 

Transistors 

Tr1, Tr2 2N2926 

Tr3, Tr4 BC108 Mullard 



Diodes 

D1, D2 

Resistors 

R1 12kO 



R2 
R3 
R4 
R5 
R6 
R7 



150kQ 

120k£i' 

12kQ 

820Q 

39kQ 

56kii 



OA5 Mullard 

R8 560-Q 

R9 10kfi 

RIO 470k£2 

R11 47kD 

R12 120kH 

R13 12kil 

R14 1MO 



R15 
R16 
R17 
R18 
R19 
R20 



2-2kQ 

nn 

1 20kO 
12kQ 
2-2kO 
10k£2 



All iW, 10% tolerance 



Capacitors 

C1 500«F 



C2 
C3 
C4 

C5 
C6 



0-03//F 
0-03//F 
0-03/<F 
0-01/fF 
(Ma*F 



C7 1-5/iF 

C8 25// F 

C9 25/jF 

C10 2-5//F 

C11 6800pF 



Circuit for Train 

Transistors 

Tr1, Tr2 

ND1 Noise diode 

D1 



Whistle No. 7 

BC108 Mullard 

Z1J Semitron (see part 1) 

OA5 Mullard 



Resistors 

R1 12kfi 



R2 
R3 
R4 
R5 
R6 
R7 
R8 



12kD 

12k£2 

2-2k-Q 

120kD 

10kQ 

1kn 

100kQ 



R9 220kD 

R10 68kQ 

R11 tOfcQ 

R12 120kQ 

R13 12kQ 

R14 4-7kQ 

R15 iokn 



R16 47kfi 

R17 2-2M2 

R18 1kfl 

R19 22k£2 

R20 220kH 

R21 39kf2 

R22 15kft 



All *W, 10% tolerance 



Capacitors 

C1 100/fF 

C2 5000pF 

C3 5000 pF 

C4 5000pF 

C5 10//F 

C6 05//F 



C7 

C8 

C9 

C10 

C11 

C12 



0-1/tF 

0'03«F 
10/jF 
0-2«F 
0-2«F 
10// F 



C13 lOyiF 



Bell Chime Circuit No. 8 

Transistors 

Tr1, Tr2 2N2926 

Tr3, Tr4 BC108 Mullard 



Diodes 

D1, D2 



OA5 Mullard 



Resistors iwatt 10% 

R1 39kn (see text) R9 47kH 

R2 10kf2 R10 470kl2 

R3 100kQ R11 12kfi 

R4 10kQ R12 120kQ 

R5 omitted R13 1M.Q 

R6 220kU R14 6800 

R7 IkQ R15 120WJ 
R8 10kO 

(Note: R5 omitted due to circuit modification) 

All *W, 10% tolerance 

Capacitors 

C1 100//F 



R16 220kO 

R17 120 

R18 120kO 

R19 10kQ 

R20 220kQ 

R21 15kQ 

R22 2-2WQ 



C2 
C3 
C4 
C5 
C6 



1//F 

0-1/tF 
2-5/<F 
0-2//F 

0-5//F 



C7 


50/iF 


C8 


0-1//F 


C9 


2-5//F 


C10 


10// F 


C11 


2-5«F 


CI 2 


0-02/jF 



the taxi horn circuit which 
should have been adjusted to 
between 200 and 250Hz. The 
pitch of the bell chime oscillator 
is best adjusted by substituting 
Rl with a variable of say lOGkH 
in series with a fixed resistor of 
not less than 18kXl, to prevent 
the base of Trl being taken 
straight to h.t.-K Pitch should 
then be adjusted until it is very 



close to that of the taxi horn 
oscillator frequency i.e., until a 
slow beat becomes audible. 
Check the amount of resistance 
in circuit and replace with an 
appropriate value fixed resistor. 
It might be better to replace Rl 
completely with a small pre-set 
of say SOkil in series with a 
fixed resistor of 18kll. Again the 
effectiveness of the sound is best 



judged aurally but the output 
waveform, if displayed on an 
oscilloscope, should appear com- 
plex and with considerable fluc- 
tuation in the amplitude of the 
harmonics. The triggering and 
output waveforms are shown in 
Fig. 21 (Bell Chime circuit wave- 
forms A, B and C.) The circuit 
hoard layout is shown in Fig. 20. 
TO BE CONTINUED 



1049 



practically 
wireless 

commentary by 




NOT the study of rustic man, 
not a thesis on triple-ended 
anchorites, nor even a dis- 
course on moonrock. Tribology is 
a word coined by the ball and 
roller bearing people, to mean the 
study of inter-acting surfaces in 
motion. 

Passing lightly over the thought 
that some tribal rites, like "Top of 
the Pops," and the "Rolf Harris 
Show," would give Tribologists 
something to study, we nod sagely 
in the direction of the scientists 
and hark back to a reference we 
made when talking about head- 
phones — computer-aided-design. 

The thought is inspired by the 
news that the Science Research 
Council has given a grant of 
£9,730 to Bath University to fur- 
ther Dr. A. W. Keen's "Computer- 
Graphics- Aided Synthesis of Elec- 
tronic Signal Processing Circuits. 
C.A.D. for short. 

Down there in rural Bath, they 
argue that circuit design has 
"grown to the point where en- 
gineers tend to collect standard 
circuits from which they can draw 
when they are designing." Doctors 
Whipp and Martin, two lecturers 
on Dr. Keen's team, nod towards 
the increasing number of devices 
such as transistors used in instru- 
ment circuits and the growing 
need for some method which will 
allow not only the selection and 
assembly of standard circuits but 
also the automatic generation of 
new electronic circuit systems for 
a desired application. 




Some tribal rites 



Now that's a thought! Toss into 
the system for /50 computer — no, 
I am wrong, with the aid of this 
grant these lads hope to further 
their researches with a PDP 8 E 
complete with graphic display, 
early this year — well, toss an idea 
in SOMEWHERE, and what comes 
out? A completely packaged, plas- 
tic-clad, printed circuit, ergonomi- 
cally engineered, probably deep- 
frozen to lock in the flavour of the 
multi-million bits. 

Beautiful, shiny, perfectly con- 
cocted — but as neutral as a con- 
scientious umpire. Bring in the 
tribological ergonomists and indi- 
viduality flies out of the window ! 
However, gone will be the kinky 
boards that could only be the 
dream-children of the Superstar 
factory, the panels from Messrs. 
Busbox with more lines to the 
inch than a miniature orchestral 
score; vanished those flexible, 
flimsy, finnicky efforts that come 
from the Yoshi-Toshi Company. 
Disappeared like yesteryear's 
wiring harnesses, all dull colours 
and knotted string and bent as 
precise as the kink in a drill ser- 
geants moustache. Declining like 
those dinky glass bottles with 
their warm and friendly glow . . . 

Forgive an old engineer. Allow 
me to wipe away a nostalgic tear. 
The thought of some of our lost 
specialities makes me sad. The 
evocative whiff of burning trans- 
formers brings back memories and 
the pungency of toasted selenium 
is a haunting signpost to the days 
when apprentices listened when 
spoken to, customers put us on a 
par with the rent collector and a 
crossover was some form of token. 

But although the keen Dr. 
Whipp or the whippy Dr. Keen 
would have us banish even more 
of the character that remains in 
radio, even though they would 
have "wireless" mean what it says, 
Henry suspects that the immu- 
table obtuseness of the average 
computer will defeat them. To 
judge by our electricity bills, de- 
mands of the telephone company 
and the current computerised 



No. 78 



Tribology 




Disappeared like yesteryear's wiring 
harnesses. 

identity by which our friendly 
neighbourhood bank manager 
knows us, all that CAD will cough 
up for the boys of Bath is a row 
of inscrutable dots. Rationalising 
of circuitry is all very well, the 
aim to restrict the prolific growth 
of semiconductor devices is very 
commendable, but we suspect that 
the ultimate result will be to add 
a number of new integrated cir- 
cuits to an already bewildering 
list. Take a look at some of those 
tuner amplifiers which already 
feature i.c.'s. Their overall cir- 
cuitry is as complicated as before, 
their designer has taken advan- 
tage of a new device to extend his 
ideas within a certain budget. He 
could do even more with building 
brick circuits. Imagine the com- 
plexity that Bodgit & Co could 
produce from a handful of i.c.'s 
and some of the Bath-bricks, a 
bunch of wires and some presets. 
The trouble is that for every 
beautiful computerised block that 
condenses the Bath team's ideas 
there will have to be twenty modi- 
fied versions to suit individual re- 
quirements or circuit designers. 
And that's the trouble — there 
will have to be a bit off here and a 
bit off there until the poor old 
computer won't know what to dis- 
gorge. Computers are notoriously 
single minded. Those whip-keen 
laddies at Bath have been talking 
to computers so long that they 
think all designs can be divided 
into logical boxes. They should 
take a look at some of the articles 
for Practical Wireless that the 
Editor dares not publish. 



1050 



.uc 




uu 



-p c-pnnrp i^irinfi'r? 



LAJ. IRELAND 



Number 18 



Digital Counting and Display Devices 



THIS month's article deals with a rather unusual 
topic in that we confine ourselves to the digital 
i.e. field which so far has not been considered 
in the present series. Yet the greatest advance in i.e. 
technology is being made in this field so that today 
relatively cheap m.s.i. (medium scale integration) 
circuits are on offer by many manufacturers making 
it possible for the amateur to construct low cost 
digital readout and counting circuits with a wide 
variety of uses. 

It may appear at first approach that there are few 
possibilities of interest in this field. Indeed due to 
the inherent cost of constructing equipment using 
discrete components it was well beyond the range of 
the average constructor but once again mass pro- 
duction coupled with the mastering of m.s.i. tech- 
nology has completely changed the picture. 

Very compact decade counters can be built for less 
than £5 per decade which compares very favourably 
with the old dekatron units which proved very popu- 
lar for any pulse counting requirements. In fact a 
maximum counting speed of around 20kHz was 
usually associated with such tubes whereas today 
there is little difficulty producing counting speeds in 
excess of 20MHz with t.t.l. logic circuits. 

Within the SN74 series of i.e's are decade counters 
and decoder drivers. Two approaches are possible 
here depending on the type of display output 
required. One incorporates a cold cathode neon type 
tube using a common anode with ten separate 
cathodes formed in the shape of the 0-9 numerals 
and stacked behind one another. 

An input pin is required for each cathode which 
in turn is usually connected to a decimal decoder 
circuit. Even though the gas filled readout tube may 
require around 200 volts for satisfactory operation, 
it is not necessary that the driver transistors be 
capable of withstanding this potential as the anode 
resistor will automatically reduce the voltage and 
limit the current through the driver transistors. Thus 
any transistor with a collector to emitter breakdown 
voltage around 60 volts will work quite well. 

A complete decade counter using the new Bi-Pak 
SN series is shown in Fig. 1. Due to the complexity 
of the decoder and driver circuits only the logic 
symbols for the various units are illustrated and the 
amateur will have to get used to the black box 
approach to complex i.e. circuits as it would be virtu- 
ally impossible to follow literally the hundreds of 
transistors and associated passive components in the 
present design. 

One drawback of the above system is the high 
voltage required for the readout tube which neces- 



+ 180V 
I 



.20k 



Numicator tube Type XN24 (Top view) 



vw 



u 



4«5V 
-ve 

— 1 <r 






15 



V9 1 4 9/ 



J5 

*L J*. 



J1 

M ft 



SN7441A 



I 1 ■ ■ ■ W P ■ ¥~ 
1 |2 3 A |5 ]6 ] 7 ]Q 



Input 2V 




Fig. 1 ; A complete decade counter using the new Bi-Pak SN series. 

sitates the use of some form of inverter if the unit 
is to be put to portable use. A more modern approach 
therefore to digital readout is the low voltage fila- 
ment type of segmented tube consisting of seven 
independent strip filaments arranged in a figure 
eight pattern. 

Any numeral between 0-9 can be found by illumina- 
ting the required segments. In fact eleven alphabet 
letters can also be created so to an extent the tube 
can be made to function as a limited alpha-numeric 

1051 






display device with suitable decoding circuits. In the 
present design consideration will be given to the RCA 
numitron type DR2000. 

The same decade counter with b.c.d. (Binary Coded 
Decimal) outputs as used in the first design will 
function here but a different decoding circuit is 

Bottom view of numitron. 
Fits into a 9 pin miniature 




Fig. 2 : Shows the interconnections of the units using the CD2S00E 
decoder. 



required. Whereas in the previous design a separate 
pin was needed for each numeral, here only seven 
are required and a b.c.d. to seven segment decoder 
is used— RCA type CD2500E. 

Once again the complexity of the internal circuitry 
of this i.e. makes it impractical to draw so Fig. 2 
shows the interconnections of the complete unit. A 
suitable printed circuit board pattern should not 
prove too difficult for the competent constructor and 
use could profitably be made of the new dual-in-line 
mounts advertised by some firms in this magazine. 
In addition to providing easy insertion and removal of 
the i.c.'s they also prevent damage to the i.c.'s from 
excessive heat in the soldering process. 

Needless to say, numerous uses can be visualised 
for these counters. The 50Hz mains can be used as a 
frequency standard to make an accurate interval 
timer when coupled through an AND gate to the 
counter. Also interruptions in a beam of light or 
pulses from a geiger tube to determine the activity 
of a radioactive sample can be counted. 

A very welcome development related to this field 
is the drop in prices of the new Gallium Arsenide 
solid state light emitting diodes. Single devices of this 
type can now be purchased for around £1.50. With 
no filament to worry about they are exceptionally 
robust and have an exceedingly long life span. Arrays 
using upwards of fifty of these arrayed in a 5 x 10 
rectangular matrix are used in many alpha numeric 
readout systems and recently the first all electronic 
solid state wrist watch with digital readout has been 
released in the U/S. using four of these arrays. If the 
present trend continues they will certainly offer 
fascinating possibilities for the home constructor in 
the not too distant future. 

IC type SN7441A and SN7490 are available from 
Bi-Pak Semiconductors. 

IC type CD2500E and numitron DR2000 are avail- 
able from: — Roberts Electronics Ltd., Hermitage 
Road, Hitchin, Herts. 

Hivac Numicator type XN24 available from: — 
Hivac Ltd., Ruislip, Middlesex. j|| 



DECCA 3000 HI-FI SYSTEM 

WON BY BRISTOL READER 

OF 25 YEARS STANDING 

A reader of Practical Wireless for 25 years has won the 
Decca Hi-Fi System Competition which was featured in 
our November issue. He is Mr. Dyke of Bristol. At a 
recent lunch held by I.P.C. Magazines to congratulate 
Mr. Dyke, it was revealed that he had taken to reading the 
magazine after the excellent results he had found with a 
home-built 2-valve radio designed by F. J. Camm, an 
earlier Editor of P.W.— and he has hardly missed an issue 
since. 

Mr. Dyke is a great fan of "Practically Wireless" by 
Henry and rates F, G. Payer amongst his most popular 
authors. Being an 'old-timer' in the construction game 
he is also a keen follower of "Going Back". 

The entry which secured the Hi-Fi System for Mr. Dyke 
was: 1-J, 2-K, 3-1, 4-E, 5-A, 6-D, 7-B and 8-C. The entry 
was the only correct one out of several thousands. 

The Hi-Fi System was something Mr. Dyke had wanted 
for a very long time and it is the first prize of any value 
that he has ever won! 

1052 




Norman Stevens on the left, Editor of Practical Wireless, congratulates 
Mr, and Mrs, Dyke on winning the Decca 3000 Hi-Fi System. 



Trojan' Tern band Transceiver 




Final Assembly When the two circuit boards and 
the panel are completed as far as is possible they 
can be fitted to the aluminium framework, shown 
in Fig. 7, forming the sides and back of the chassis. 
The back has a hole for the outlet of the power 
supply cable form and another to allow adjustment 
of the transmitter mixer anode coil L4. The co-axial 
aerial socket is the only fitting on the back member. 
In practice only the side members were fitted 
initially the back not being fitted until the transceiver 
was completed and aligned, the co-axial socket being 
allowed to float in the meantime. This allowed full 
access to the chassis, another advantage of this 
method of construction. 



PART TWO 



ERIC DOWDESWELL 
G4AR 



headphone and key jacks. The four switching diodes 
D3-6 are mounted on a piece of Veroboard and fitted 
close to the key jack. 

The main tuning capacitor VC2 is mounted on a 
small aluminium bracket across the cutout in the 
left hand board and a certain amount of "packing" 
with washers may be found necessary to ensure that 
the spindle lines up with the tuning drive coupler. 

The wiring between the panel components and the 
boards may now be completed and a general check- 
over of all the wiring made for short circuits or 
errors. 

Power Supply Unit The circuit of the supply unit, 
Fig. 3, shows that the transformer Tl provides the 
h.t, the negative bias for the transmitter and the 
relay operating voltage as well as the heater supply. 
On the h.t. side choke input is used in order to 
improve the regulation and to keep the voltage 
down to around 270V so avoiding the use of waste- 
ful dropping resistors. 

Switch S2 is mounted on the back of the unit 
and is essential during the alignment procedure for 
cutting the h.t. to the p. a. The speaker is a 4in. one 
with a matching transformer T2 and slide switch S3 
cuts out the speaker when headphones are being 
used. 



6x3 
16SWG. Aluminium 




6x3" 

16SWG Aluminium 



Fig. 7. Exploded view of chassis 
members. Note that panel extends 
below the bottom of the chassis, see 
Fig. 6. Part One. Since the rear member 
carries only the coaxial socket it can be 
left off until all wiring and construe' 
tional work is completed. 



The boards are attached to the chassis with self- 
tapping screws, two along each edge except at the 
front. An aluminium bracket supports the two boards 
at the centre of the chassis and is bolted to the front 
panel and the back member. This can be seen clearly 
in the photograph of the underside of the completed 
transceiver. 

The remaining components can now be fitted to the 
panel, namely the r.f gain control VR1, Q multiplier 
tuning capacitor VC4, i.f. gain control VR2 and the 



In wiring the two low voltage windings in series 
regard must be taken of their relative phase to 
ensure that the voltages are additive and reversing 
one winding if the relay operating voltage is low. 
The diodes and resistors are mounted on the bottom 
of the unit on a piece of Veroboard as can be seen in 
the photograph of the unit. 

The eight leads from the transceiver are taped 
together and fitted to an octal plug, the leads being 
about twelve inches long. The receptacle on the power 

1053 



unit is an ordinary octal valveholder. Note that the 
earth lead is duplicated to reduce the resistance of 
this lead. 

A speaker fret 6 3 4 x 5*$n. in grey plastic (G. W. 
Smith Ltd.) was bolted to the panel of the power 
unit, part of the fret being cut away as shown in the 
heading photograph in Part One of this article. The 
cabinet was finally sprayed with a grey enamel to 
match the transceiver cabinet and panel. 

ALIGNMENT 

Before alignment, checks should be made to ensure 
that the various h.t., bias and heater voltages are 
approximately correct. Initially the transmitter valves 
V5, V6 and V7 can be removed. The i.f. gain control 
is set at half way and the b.f.o. and first oscillator 
coils L2 and L3 shorted out, as is the diode D2 in the 
product detector. The Q multiplier valve V8 can also 
be removed temporarily. 

Connect a low reading a.c. voltmeter across the 
primary of the output transformer via a blocking 
capacitor of about 0-ljtF. Feed a modulated signal 
at 465kHz from a signal generator to the grid of the 
second i.f. amplifier V4 and adjust the cores of i.f.t.3 
for maximum output, at all times keeping the signal 
input as low as possible consistent with a reasonable 
output meter reading. 

Transfer signal to grid of V3 and repeat tuning 
procedure with i.f.t.2 finally feeding the signal to 
V2 and peaking i.f .LI. Without changing the fre- 
quency of the input signal on 465kHz switch off its 
modulation, remove the short circuit from the b.f.o. 
coil L3 and the diode D2 and tune the core of the 
b.f.o. coil until a beat note is heard which should be 




A close-up of the main tuning mechanism. Note cut-away dial plate 
to clear potentiometers and mounting bracket for VC2. 



adjusted to zero-beat with the input signal. 

The next step is to adjust the first oscillator for full 
coverage of the Top Band, i.e. 1-8 to 2-OMHz. 
Remove the short circuit from the coil L2 and feed in 
a modulated signal of l-8MHz to the grid of the 
mixer valve V2 again shorting out the b.f.o. coil and 
the diode D2. With the main tuning capacitor VC2 

1054 



near to maximum capacity adjust the core of L2 
until the signal at l-8MHz is heard. The oscillator 
itself should now be on 2265kHz which must be 
checked with a dip oscillator. 

Turn the dial so that the capacitor is near minimum 
and feed in a signal at 2-OMHz and adjust trimmer 
TCI until the signal is heard. These last two steps 
must be repeated until the required coverage is 
obtained. 

RF Stage With the r.f. gain control about half way 
feed in a signal to the aerial socket at l*9MHz and 
swing the p. a. tuning capacitor VCla-b remembering 
that this peaks both the p.a. circuit and the 
receiver mixer grid circuit. It will be found to peak 
the 1 • 9MHz signal at two points on the dial corre- 
sponding to these two circuits. Adjust the core of LI 
until the two peaks coincide when VC1 will be 
found to be near maximum capacity. 

Q Multiplier The Q multiplier valve V8 can now 
be replaced. With the receiver working normally 
choose a quiet spot on the band with no signals and 
with the Q multiplier tuning control VC4 at mid 
point and switch S2 in the "peak" position tune the 
core of L7 until the; background noise is at its lowest 
pitch. The selectivity control VR3 should be set at 
minimum. 

If VR3 is now rotated a point will be reached when 
the stage will go into oscillation. On tuning in a 
signal the Q multiplier tuning control can be adjusted 
to peak the beat note at the same time increasing 
the selectivity control to just below the point of 
oscillation. 

Without altering the main tuning dial any signal 
in the passband can be peaked, the maximum select- 
ivity being just about all that any c.w. operator 
could desire. 

With S2 in the "null" position interfering signals 
can be severely attenuated with the Q multiplier 
controls. 

Transmitter Mixer Valves V5, V6 and V7 may now 
be replaced. Since the b.f.o. and first oscillator are 
now on their correct frequencies it is very likely that 
an indication of grid current will be shown on 
pressing the key. Switch SI must be set to read grid 
current and the h.t. to the p.a. switched off. 

The cores of the transmitter mixer and buffer 
amplifier coils L4 and L5 can now be adjusted to 
peak the grid current at the centre of the band 
and should reach around 3mA. Check and double 
check that the output is on Top Band using an 
absorption wavemeter. 

A dummy load carbon resistor of between 50 and 
70 ohms should now be connected to the aerial socket. 
This resistor should have a power rating of at least 
5 watts. and may br» made up of several higher value 
resistors in parallel but they must be of carbon and 
can be mounted on a coaxial plug for convenience. 

Turn the p.a. loading capacitor VC3 to maximum 
and peak signals with the p.a. tuning control. On 
pressing the key the anode current will be about 
45mA and the p.a. tuning should be quickly tuned 
for a dip in anode current to about 20mA. Decrease 
the value of the loading capacitor and re-dip the 
tuning. Repeat this until the dipped value of the 
anode current is about 35mA. This represents an 
input of about 10W, the legal maximum on Top Band. 
Check again that the output is on the correct fre 
quency using the absorption wavemeter. 



i 



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61 HIGH STREET, BEDFORD. Tel. 0234 52367 



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1055 



BRAND NEW 
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32iP 
37iP 



2M1090 22) p 

3SI091 SSip 

2N1131 SSp 

2N1132 SSp 

2K1302 17ip 

2N1303 17Jp 

3X1304 22 Ip 

2N1305 BSlp 

as 13 08 SSp 
2N1307 
2N130S 
2NI309 

2S1507 171p 

2S1613 BSp 
3S1631 

smks 

2SIM7 

2N-JF13S 27ip 

2X11139 B7iP 

2S1711 25p 

2X1 i HKSl SBip 

2N1893 37ip 

2X2147 SBlP 

2X2 148 67 jp 

3X21S0 57ip 

SN-.'llta 40p 

2N219.1A 4B1P 

2X2194A 80P 

2X2217 B7Jp 

2X2218 SSlP 

2X2219 32 |p 
2X2220 
3X222 1 
2N2222 
2N2287 

£1-071P 

2X2297 30p 

8912368 171P 

2X23B9 171P 

2X2369 A 171P 

2X3410 481P 

2X2483 B71P 

2X24 H 4 381P 

2N2539 S2iP 

2N2540 £2iP 

2X2613 SSP 

2S2614 30p 

2X2046 57 tp 

■2X2rt«n 3Btp 
2S2711 
2X2712 



25B 
30j 
30b 



35p 
30p 
SOp 



26p 
25 p 
30p 



zip 
£5p 



2X2713 871 p 



2X27H 
2X286S 
2X2904 
2S2904A SSip 
2H2UOB 37ip 
2X2'.ni;,A 40p 
2X2 Wirt 25P 
2N290IIA 27ip 
2X2907 SOp 
2N2923 
2X2924 
2X2925 
2X2926 
Green 



SOp 
SSip 
SOp 



lEp 
15p 
15b 



14p 
Yellow ISip 
Orange 12 ip 
2X301 1 SOp 
2X3014 3B1P 
2X3053 25p 
2X3054 
2X3055 
2X3133 
2X3134 
2X3135 
2N3136 
2X3390 
2S 3391 

2X3391 A SOp 
2X3392 17 *» 
2X3393 15b 
2X3394 15p 
2X3402 BSiP 



SOp 

75p 

SO? 
30p 
25p 
25p 
25p 
20p 



2X3403 22 IP 

2 X: 34 04 32ip 

2X3465 45p 

2X3414 BBlp 

2X3415 22ip 

2X3416 871p 

2X3417 37ip 

2X3570 41-25 

2X3572 97J-P 

2X3605 Z71p 

2N"3m»6 87lP 

2X3607 BBlp 

2X3702 121p 

2X3703 121p 

3S3704 171p 

2X3705 ISp 

2N.170H ISip 

2X3707 ISp 

2X37 OH OBp 

2X3769 lOp 

2X3710 lip 

2X3711 12p 
2X3715 £2'22i 

2 N 37 16 £2.00 

2N3791 £2.75 

2N.1H19 SSp 

2X3623 07ip 

BH3884 B71P 

BN38S4A £7iP 

2X3-S55 27 1 p 

2X3655 A SOp 

3X3860 80p 

2S38CtlA S6p 

2N3868 B6p 

2XHK56A SOp 

2X3H59 B7ip 

2X3859 A 321 P 

2X386(1 SOp 

2X3866 £1.50 

2X3877 40p 

2X3*77 A 40p 

2X3900 37 ip 

2X3900 A 40p 

2X3901 fl7lp 

2X3903 SSp 

2X3904 SSp 

2X3905 B71P 

2X3906 37lp 

2X4056 171p 

2X4059 10P 

2X4066 ISlP 

2X4061 lfiip 

2X4062 lBlp 

2X4244 47 Ij 

2X4285 17JP 

2X4288 17 iP 

2X4287 171P 

2X42H9 17iP 

2X4289 171p 

2X4290 17iP 

2X4291 171p 

2X4292 lBlp 

2X4303 47iP 

2X5027 SSlP 

2X5029 67 IP 

2X8029 47 tP 

2X5030 4B1P 

2X5172 lBlp 

2Xfil74 SSjP 

2X5175 BBlp 

2X0176 45p 

2X5232A SOp 

2X5245 4Bp 

2X5246 tBip 

2X5249 87H> 

2X5265 £3-25 

2X5266 £2-78 
2X5267 £2'82i 

2X5308 B71p 

2X5306 40p 

2X5307 37lp 

2X5306 871p 

2N5309 B2ip 

2N6310 4*1 p 

3X5354 B71p 

2X5355 87ip 

3X5356 32 ip 

2X5365 471p 

2X5366 32ip 

2X5367 87 ip 

2S5457 37 I p 

28005 7Bp 

28020 £2-00 

38102 GOp 

28103 28p 

28104 25 p 
23501 38 iP 
285112 SSp 
28503 B7lP 
3XS3 40b 
3X128 70p 
3S140 771P 
3X141 721p 
3X142 SSp 
3S143 67 ip 
3X152 S7Jp 
K.C.A. 52iP 
4 0050 SSp 
40251 32 jp 



40309 

40310 

40311 

40313 

40314 

40320 

40323 

40324 

40326 

40329 

40344 

40347 

40348 

40300 

40361 

40 3 62 

40370 

40400 

40407 

404 06 

40410 

40467 A 

40408 A 

40600 

AC 107 

AC126 

AC127 

AC128 

AC 154 

AC 178 

AC187 

AC188 

ACT 17 

ACT 18 

ACY1S 

ACY20 

ACY21 

ACY22 

ACY28 

ACY40 

ACY41 

ACY44 

AD 140 

AD 1 49 

AD 150 

AD161 

AD162 

AF10S 

AF114 

AF115 

AF116 

AF117 

AFH8 

AF119 

AF124 

AF125 

AF126 

AF127 

AF139 

AF178 

AF179 

AF180 

API 81 

AF239 

AF279 

AF280 

AF211 

A8Y26 

A8Y27 

A8Y28 

ASY29 

A8Y36 

A8Y60 

ASY01 

A8Y54 

ArtYKti 

A8Z20 

A8Z2I 

ACY10 

BC107 

BC10S 

BC109 

BCU3 

BC115 

BC116A 

BC118 

BC121 

BC122 

BC125 

BC13S 

BC140 

BC147 

BC148 

BC149 

BC152 

BG167 

B'.'15M 

BC159 

BCI60 

BC167 

BCI68B 

BC168C 

BC169B 

BC169C 

BC170 

BC17I 

BC172 

BC176 

BC1S2 



S21P 
45p 

SSp 
47*p 
S71p 

47ip 
32iP 

mi 

37*p 
SOp 
27ip 
S74P 
82ip 
42 t p 

mv 

mv 

321p 
57ip 

40p 
52iP 
82ip 
S71p 

SSp 
S7ip 

30p 

aop 

25p 

20p 
22jP 

25p 
S2tP 
S7ip 
E7ip 

2Sp 

2Sp 

esp 

SSp 
20p 
20p 
SOp 
SSp 
40p 
SStP 
87ip 
62ip 
S7ip 
871p 
4Stp 
25p 
SOp 
SSp 
SSp 
S2*p 
2 Op 
22ip 
SOp 
£0p 
17tp 
87tp 
42 t p 
7StP 
82ip 
42tp 
42ip 
47tp 
62ip 
S2iP 
25p 
S7ip 
27*P 
27ip 
S5p 

esp 

SSip 
SSp 

SBip 
87ip 
42] P 
£1.80 
12*p 
12iP 
IStP 
27ip 
40 
871p 
SSip 
SOp 
SOp 
SSp 
SSp 
S7ip 
17*P 
1B1P 
17Jp 
17^p 
20p 
171P 
£Op 
«2Jp 
ISp 
14p 
ISp 
1*P 
ISp 
ISlP 
IBp 
IBp 
22jp 
12tP 



J3C1H3 

BC184 

BC212L 

BCY80 

BCY31 

BCYSa 

BCY33 

BCY34 

BCY38 

BCY39 

BCY40 

BCY43 

BCY43 

BCY54 

BCY5S 

BOYSfl 

11CY60 

BCY70 

BCY71 

BCY72 

Bczm 

BCZll 



125P 
ISp 
ISip 
S7lp 
27!p 
87lp 
SOp 
224 p 
22*p 
S2lp 
37iP 
ISp 
ISp 

aatp 

22ip 
22jp 
97H> 
20p 
42ip 
17ip 
27ip 



BD116 £l-12i 
BD131 6Sp 



UDI23 
BD194 

BD131 
Bl)!3> 



82ip 
60p 
971P 
97jp 



BDY10 £1-371 
BDV11 £ 1-621 
BDY17 £1-50 
BDYlfl £1-78 
BDYlfi £1-B7i 
J'.T>\".:0 £1-121 
BDY38 971P 
BDY80 " 
BDY61 
BDY62 
BF11 



BF117 
BF133 

BFI67 

BF17a 

BF177 

BF17H 

BF179 

BF180 

BF181 

BF184 

BF185 

BF194 

BF195 

BF196 

BF197 

BF198 

BF200 

BF224 

BF225 

BF237 

BF238 

BF244 

BFWB1 

BFX12 

BFX13 

BFX29 

BFXOT 

BFX42 

BFX44 

BFX68 

BFX84 

BFX80 

BFX86 

BFX87 

BFX88 

BFX8H 

BFX93A 

BFY10 

BFY1 1 

BFY17 

BFY18 

BFY19 

BFY20 

BFY21 

BFY24 

BFY28 

BFY26 

BFY29 

BFY30 

BFY41 

BFY43 

BFY50 

BFY81 

BFY52 

BFY63 

BFY66A 67 t p 

BFY7B SOp 

BFY76 

BFY77 

BFY90 

BFW58 

BFW56 

BFW60 

BFX25 

BPX29 

BFY10 

BRY39 

B8XI9 

B8X20 

B3X21 



£1-25 
£1-25 
£1-00 
25p 
47tP 
S71P 
25p 
321b 
32ip 
521P 
72 ip 
35p 
32Jp 
25p 
*2lP 
171p 
20p 
42*P 
4Bip 
421p 
B2ip 
SOp 
SOp 
221p 
S21p 
32 ip 
47Jp 
22ip 
221P 
SOp 
SOp 
871p 
371p 
674p 
SSp 
32ip 
28p 
S7ip 
2Sp 
821P 
70p 
321p 
421p 
221b 
32lp 
321P 
£1-80 
421p 
4Sp 
SSp 
SOp 
SOp 
SOp 
SOp 

asip 

22tp 
.... ; 
22jp 
17,p 



4£lp 
57tp 
B71p 
S71P 
SSp 
SSp 
£1.88 
£1-B0 
£148 
47, p 
17ip 
171P 
37jp 



118X26 45 p 
B8X27 47lp 
B8X2S 321P 
B8X60 821P 
BSX61 821P 
B8X76 S21P 
B8X77 S71P 
B8X7R E71P 
B8Y10 271P 
BSY11 27 IP 
B8Y24 15p 
B8Y25 ISp 
B8Y20 17|p 
B8Y27 17 Ip 
B8Y28 17ip 
BXT2® 17 IP 
B8Y32 25p 
BSYS8 25p 
B8Y37 25p 
B3Y38 221p 
B9Y39 221P 
BSY46 321P 
BSY51 3B1P 
B8Y52 S21P 
B8Y53 371P 
B8Y54 40p 
B3Y56 BOp 
B8Y78 47 IP 
B8Y79 4Sp 
B8Y82 82 (P 
B8Y90 B71P 
BBY96A IBiP 
B8W41 421P 
BSW70 271P 
C1U 7Sp 

C424 B74fl 

C42B SSp 

C426 40p 

C428 87 Ip 

C744 SOp 

D10P1 871p 
D18P2 40p 
D16F3 87 IP 
D16P4 40p 
GET102 SOp 
QET1IS 20p 
GET1I4 SOp 
OKT118 20p 
GET119 BOp 
GET 120 8B1P 
GKTR73 121P 
OET680 80p 
GETB87 BOp 
GET989 S21P 
GET890 2S1P 
GET896 221 p 
GET807 28 IP 
OET898 22ip 
MJ400 £1.071 
MJ420 £1-121 
MJ421 £1,121 
MJ430 £1-021 
MJ440 BSP 
MJ480 87 IP 
MJ48I 11.25 
MJ490 £100 
MJ491 (1-871 
MJ180O £2-171 
MJK340 82 IP 
MJE520 874P 
MJE521 871P 
MPF102 4B1P 
MPF103 87 IP 
MPF104 871p 
MPF105 371P 
MF836S8 381P 
XKT0613 47JP 
XKT124 421P 
XKT12S 27iP 
SKT126 S71P 
XKT128 B71P 
SKT138 271P 
NKT137 SBlP 
SKT210 SSp 
NKT211 30P 
SKT212 SOp 
XKT213 SOP 
XKT214 Bglp 
XKT215 ESlP 
XKT216 S71P 
XKT217 421P 
SKT219 SOp 
XKT223 S71P 
SKT224 SSp 
XKT325 2S1P 
XKT229 SOp 
SKT237 SBp 
NKT238 SBp 
NKT240 E71P 
XKT24I B71P 
SKT242 80P 
XKT243 S21P 
SKT244 I71P 
XKT245 EOp 
SKT281 BOp 
XKT269 SOp 
XKT264 BOP 
SKT371 SOP 
SKT273 SOp 



XKT274 20p 
XKT275 SOp 
XKT231 B71P 
XKT401 871p 
XKT402 90p 
XKT403 75p 
XKT404 821P 
XKT405 75p 
XKT406 821p 
XKT451 B21p 
XKT462 82lp 
XKT453 47lp 
XKT603FS21P 
NKT613F381E 
XKT674F SOp 
SKT077F 30p 
SKT733 BOp 
XKT781 SOp 
XKT10419S0P 
XKT10439 

871P 
NKT10519 

32}p 
XKT20329 

*7ip 
NKT20339 

871P 
XKT80111 

771p 
XKT80112 

97JP 
SKT80113 

£1.18 
XKT80211 

821 P 
XKT60212 

921p 
SKT80-213 

0B1P 
NKT80314 

mv 

XKTH0215 

B2ip 
SKT80216 

924p 



OC20 
OC22 

OC23 
OC24 
OC25 
OC26 
0C2« 
0O29 

ocas 

OC36 
OC41 

OC42 

O044 

OC45 

OC46 

0C70 

OC71 

OC72 

OC74 

OC75 

OC76 

OC77 

OC81 

OC81D 

OC83 

OC84 

OC139 

OC140 

OC170 

OC171 

OC200 

OC201 

OC202 

OC203 

OC204 

OC205 

OC207 

OCP71 



7Bp 
SOp 
SOp 
SOp 
421P 
S7ip 
8S1p 
621p 
GOp 
621P 
SSip 
SSp 
SOp 
121P 
ISp 
ISp 
121p 
121P 
SSlB 
B21p 
B2VP 
SOp 
SOp 
22lB 
SSp 
SSp 
32iB 
32ip 
SOp 
SOp 
371p 
471b 
SSip 
421P 
421P 
«21p 
7Sp 
421p 



0RF12 SSip 
OBPfll BOp 



FS46A 


SBlP 


TI834 


S21p 


TI843 


40p 


TT844 


mi 


TI845 


ISip 


TIS4B 


ms 


TI847 


IBlP 


TI848 


ISip 


T1B49 


12ip 


TI8S0 


171p 


TI881 


iaip 


TI8S2 


IStp 


TI853 


221P 


TIS80 


££1P 


TI881 


25p 


TI882 


S71p 


TIP20A 


SOp 


TIP30A 


eop 


TIP31A 


«2)p 


TIP32A 


7Sp 


T1P33A 




Sl-tffiip 


TIP34A 


IB-OS 



PANEL METERS 

38 Berica— FACE 8IZF. 42 X 42mtn. All prices fti 
B.C. 

Mliroamp £1-871 sn 

£1-76 



Pose & Pickirii lOp per order. Europe ISp. Commonwealth (Air) SSp (HIN.) 



100 
200 
5 .'0 

30-0-SO 
1 '10-0- 160 
500-0-000 

i 



£1-62} 
G-37J 
£1-75 
£1-82* 
£1-BS 
Mil irirup fl-SS 
(1-B8 
£1-25 



50 
300 
500 



■1-9 pieces. All iiieUra 

Mill lamp £1-28 

£1-25 

Sl-25 
Amp £125 

£1-28 
Volts £1-25 

£1'2S 

£1-26 

fl'BS 

£125 



SILICON RECTIFIERS 

FIV 50 100 200 400 600 806 

1A lOp 12iP ISp 18p 17ip I9p 

3A 18p — — 2SJP — SOp 

6A — - 25p SOp S21p 3Sp 

10A — GBJp 87ip SSp 77Jp 86Jp 

17A — B7J p 621p 77 J p BOp 97 ip 

*8 amp on!y. 1 amp are plastic enc&pKUlatloD. 



1000 1200 
20p — 

SOp — 

97 Ip £1-25 

£1-20 £1-67 J 



1X914 07ip 

1X916 07ip 

IN" 4007 22jp 

I 94 4 lOp 



18113 
181 20 
18121 
19130 
18131 
18132 
1M940 



ISp 

ISp 

171P 

12ip 

12iP 

ISp 

07ip 



AAU9 10p 

AA129 lOp 

AAZ13 lOp 

AAZ15 121 p 



DIODES & 

A '/IT ISip 

B.UOO ISp 

BA102 22)p 

iiuiii S21p 

BA115 07lp 

BA141 32 jp 

BA142 321 p 

BA144 121 p 

B 1145 20p 

K US 4 121P 

BAX13 IBip 

BAX16 181P 

BAY18 171p 

BAY31 07)p 

11117- 12i p 



RECTIFIERS 

BY 100 17 Ip 
BY103 221P 
BY122 871P 
BY124 ISp 
BY126 ISp 
BY127 17 1 P 
BY164 S7ip 
BYXIO BSlp 
BYZ10 SSp 
BYZ11 32 |p 
BYZ12 SOp 
BYZ13 25p 
F8T3/4 22|p 
OA5 17 ip 

OA10 S2)p 



0A9 


lOp 


OA47 


071p 


OA70 


071P 


OA73 


lOp 


OA78 


09p 


OA81 


07lp 


OA85 


071p 


OA90 


071P 


0A91 


o-;ip 


OA95 


071p 


OA200 


lOp 


OA202 


lOp 



MA1KS THANSFORBIEBa _ , 

1 amp Charger. Sec, 1-3-5-9-18 V . , 97lp 

2 amp Caarger. Sec. V-3-5-9-18V ,. .. IMRjt 

1 amp (Doutrlas) M'l .03 Sec. tappings frnm OV to SOV **'?£? 

2 amp (Douglaa) MT 104 See. tappings Irom 6V to 60V . . £2-121 
Pott and parking 22 J p on all Transtormers. 

amp (Dougltw)) MT .07 See. tappings from 6V to 60V . . . . £8-80 

Pott and packing 371p 

VarfoUH other DougG^ Transformer* ranging from 1A to 5 A in stock. 



TBIACS 

8C41A 6 amp 100V . . 
BC41B 6 anra 200V . . 
8C41D 6 amp 400V . . 
SCSOD 15 amp 400 V . . 
40612 TO-5 mod. 6 arup 400V 
40430 TO-66 6 amp <00V 
40488 TO-5 mod. 8 amp 400V 

Economj- Range Trims 
TC4/10 (Prefsflt) 4 amp 10O FIV 
TC4/20 (Pressflt) 4 at up 200 PIV 
TC4/40 {Pressfit) 4 amp 400 PIV 
ST2 DIAC 

SCOTCH CASSETTES 0-60 SSip 

NOJl.MAL PRICE 89| p. OIR PRICE SOp 

SCOTCH Sin TRIPLE PLAY BOOIt 

SOED AL PRICE 11-B4. OUR PRICE 90p 

PLEASE NOTE: Lf RGE RASGE OF I.C.s SOW IX BTOCK. 
BEXD 6p FOR PRIOE LIST 



£1 

£1-10 
£1-20 

£2.06 

fl-45 

t71p 

SSp 

78p 

85p 
97, B 



THYRISTORS 

FIV SO 100 200 300 400 
1A B8p B7ip 87, p 40p 471p 
4 A 47ip SSp 67 iP — 77tp 
BA — SSp BSji — 75p 
7A — S6p 6S|1 — 071P 
TTC47 0.6 amp. 200 I' IV SSp. 
Also 12 amp. 100 PIV 7Sp 
2X352S at (1.271P 
VEROBOARD 



(i-r. 



Matrix 

w 

21|> 
B7jp 
86m 



0-1 
Matlii 
SOp 
S4p 
24p 
27ip 



21 X 3! Ii 
21 X Sin 
31 x 3Iin 
31 * Sin 
S X 17 in (Plain) 
Vero Pimi (Bag of 60; SBp 
(Bag of 100) 40p 
Vero Cutter 46p 

fin Insert Ion Toots (-1 and >15 
matrii) at SSp. 

HEAT SINKS 

4-8 x 4 x lin Finned for Two 
TO-3 Trans., 47*p. 411 X 2 x 111 
Finned, for One TO-3 Trans., 
SSip. for BO-1. Blp. For TO-5, 
8p Finned. For TO-18, Sp 
Finned. For TO-18, 1 - Finned. 

RESISTORS 

Carbon Film 
i nit 6%, Ip. 
t watt 6%, Up. 
1 watt 5%, Sp. 

1 watt 10%, Sip. 

2 watt 10%, Sp. 



CAPACITORS 

A large and comprehensive 

range available: Electro I Ftlc, 

Polyester, Ceramic, P0I7- 

ntyrene, 811-rer Mica, Tantalum, 

Trimmers, Tuners. 

Examples: 

2,000mF 25V, 42 J p Most 

2,500mF 50V, B71p MiUlard 

3 . <: ><" in F 25 V , SB Ip E 1 ectru 1 y 1 1 1 J 

5,000mF BOV, B71p In stock 

WIRE-WOUKD RESISTORS 

2 -S watt 5% (up to 270 ohms 

only). 7ip 
5 watts 5% (up to 8 -2k fl only), lOp 
10 watt 8% (up to 25k[l only), 

UlP 

POTENTIOMETERS 

Carbon: 

Log. and Lin., less switch, ISp. 
Log. and Lin., with switch, SSp. 
Wlre-wonnd Pots <3W). 321 p 
Twin Ganged Stereo Pots, 1-og . 
andLin.,4SlP. 

PRESETS (CARBON) 

0.1 Watt. Sp 

0.2 Watt Sp 

0.3 Watt 71 p 

THERMISTORS 

R33 (8TU) §1.871 TA3703 87|p 
K151 (Ik) l£ip 
Mul.arJ Thermistor! also in 
■took. Please emu Ire. 



Tel. 01-452 01 61/2/3 
Telex 21492 



Send Sp for new Comprehensive Semi 
conductor and I.C. list (24 pages). 



A. MARSHALL & SON 

28 CR1CKLEWOOD BROADWAY, LONDON, N.W.2 



CALLERS WELCOME 
HRS, 9-5.30 Mon-Sat 

Thur. »-l 



1056 




If it is found that the dip in the anode current 
on transmit does not quite coincide with the position 
of the p,a. tuning for maximum signals on receive, 
the transmitter should be carefully tuned and signals 
then peaked by adjusting the core of the receiver 
mixer coil LI. This should be done around 19MHz 
when it will be found that the alignment will hold 
over the whole band. 

Once the transceiver has been aligned and the 
output frequency checked and found correct the r.f. 
output indicator can be used for tuning up the trans- 
mitter. 

Final Alignment When the transceiver is working 
properly in all respects the whole alignment pro- 
cedure should be repeated and although this may 
sound quite formidable in fact it takes only a few 
minutes. 

In particular the tuning of i.f.t.l will have been 
upset by the addition of the Q multiplier stage. 

NOTES 

As the finished chassis is a close fit in the cabinet 
the flanges on the sides of the cabinet must be cut 
away to provide clearance. 

Holes are cut in the back of the cabinet, one to 
clear the power lead octal plug and the other for the 
co-axial aerial socket. Chassis cutters of l^in. and 
3 4in. respectively were used for this purpose. 

Aluminium angle trim was glued to the bottom 
front edge of the transceiver cabinet and the power 
supply cabinet, as a finishing touch, as well as to lift 
up the fronts of the units from the table. Conven- 
tional rubber or plastic feet can also be used to 
achieve the same effect. 

Letraset was used to make up labels for identifying 
the various panel controls, switches etc. 



Betow-chassls view of transceiver. 
The main components may be identi- 
fied by referring to Fig. 5. Part One. The 
inner edges of the boards are supported 
by the aluminium bracket running 
vertically downwards in the centre of 
the chassis. 



If the receiver only is re- 
quired there is no reason 
why this part of the trans- 
ceiver should not form a 
project on its own. In this 
case the cathode returns of 
the r.f. stages should be re- 
turned to earth and the p. a. 
coil L6 replaced by a Denco 
Range 3 aerial coil. 

The transmitter portion of 
the transceiver can be uti- 
lised on its own by feeding 
outputs from the first oscil- 
lator and the b.f.o. of a Top 
Band receiver into the trans- 
mitter mixer valve V5. Re- 
' member that any interference 
with these oscillators will 
affect their calibration. Other 
arrangements would have to 
be made for the changeover 
from receiver to transmit. 

Although a higher voltage 
on the p.a. would be desir- 
able from the point of view of efficiency by using 
a capacity input filter in the power supply it was 
decided to stick to choke input for the better voltage 
regulation that it provides. 

The importance of using a calibrated absorption 
wavemeter for checking the transmitter output can- 
not be too highly stressed. It must be remembered 
that the r.f output indicator will respond to any r.f. 
output including any spurii which may occur during 
alignment. 



R20 

Ik 




0A91 ! OA91 | 07 * C26 



-»-HT+ 



» ^C19 ^f"C21 TC23 

•i, J 10 I 470 I 470 

1 z± 

"In f I m 



>R25 
;6-8k 



'Mh 



R26 
470k 




Earth 

Fig, 8. Modification for reception of a.m. signals. One pole of a slide 
switch shorts out diode D2, the other pole opens the h.t. feed to the 
b.f.o., V4. Existing feed to b.f,o. must be broken at point X. 



1057 



MODIFICATIONS 

Since completing the transceiver the following 
modifications have been made to improve its 
versatility. 

AM Reception As it stands the transceiver can be 
used to receive a.m. signals by tuning the carrier to 
zero-beat. This is not entirely satisfactory so a double- 
pole changeover slide switch was fitted to the panel. 
One pole is wired in series with the h.t. line to the 
b.f.o. and the other is wired across the product 
detector diode D2 which is shorted out on a.m. Thus 
on a.m. the b.f.o. is off and Dl becomes a normal 
diode detector, Fig. 8. 

AM Transmission In order to be able to use a.m, 
telephony an open circuit jack socket was fitted to 
the back panel of the power supply unit and con- 
nected in parallel with the transmitter h.t. supply 
switch S2. 

With the switch open the output of a small modu- 
lator can be plugged into the socket and the trans- 
mitter adjusted for proper modulation in the usual 
way. 

When receiving a.m. signals the Q multiplier 
selectivity control may need backing off to obtain 
adequate bandwidth for reasonable speech quality. 

It is important to note that when transmitting in 
the a.m. mode the b.f.o. must be on. The slide switch, 
mentioned above, must be moved to the "on" or 
"c.w." position before pressing the key to transmit. ■ 




mmiu 




THE 



'It's the man from the G.P.O. about your party-political 
broadcast" 



MW 



COLUMN 



tiiiiiiiiiniin^ 

CENTRAL USSR and its Asiatic Republics to 
the south are usually neglected by the 
medium wave enthusiast. Local broadcasting 
in this area is on European frequencies and since 
the time zones are ahead of GMT, the majority of 
stations will have signed off before interference 
from Western Europe subsides for the night. 
Although there are a few all-nighters to be heard 
the best time for DX is at sign on, which occurs 
between OlGOhrs and 0300hrs GMT. Saturday night 
is unfavourable owng to the extended schedules of 
many Europeans. Harold Emblem of Mir field, York- 
shire, has been DXing this region and reports recep- 
tion of Gorki on 827kHz; Simferpol Crimea 1313kHz 
(which was heard behind Sfavanger at 1800hrs); 
Kharkov 1322kHz at 0240hrs; Saransk 1061kHz. DX 
logged recently by the writer includes Murmansk 
Lapland 656kHz at 2330hrs GMT; Ufa Bashkir 
692kHz at 0I06hrs; Kuybyshev 809kHz at 0140hrs; 
Garm Tadzhikistan 980kHz at OOSOhrs; Baku Azer- 
baijan 1016kHz at 0130hrs. Those heard signing on 
at 0200hrs GMT were Yerevan Armenia 863kHz: 
Stavropol Caucuses 881kHz and Tbilisi Georgia 
1043kHz. Others logged later in the night are Astra- 
khan 791kHz at 0206hrs; Markhagkala Dagestan 
917kHz at 0205hrs; Tashkent Uzbekistan 1025kHz at 
0230hrs. From nearby Iran, Tabriz 645kHz is often 
strong when it signs on at 0228hrs with a haunting 
Iranian melody played on a vibraphone, followed 
by a 3-pip time signal and the call 'Radio Iran.' 

Identification can sometimes be a problem with 
USSR stations. Those that do identify locally use 
the word Govarit if in Russian, Geplevar in Turk- 
men! an, Danishir in Azerbaijanian, Khosum in 
Armenian followed in each case by the place name. 
Radio Tashkent identifies in Uzbek with Tashkent- 
dan Gapiramis. Harold points out that the BBC 
transmissions in Russian on 809kHz might be mis- 
taken for Kuybyshev, but USSR stations usually 
transmit the 'Midnight in Moscow' interval signal 
two minutes before the hour or half hour, followed 
by a 6-pip time signal, while many carry the Tro- 
gramma Mayak' which is mentioned in the identifi- 
cation. Sometimes a station broadcasts on one of 
the Tropical Bands as well as on the MWs. The 
writer has checked Ashkhabad 200kHz on the long 
waves against Ashkhabad 4825kHz on the 60 metre 
band and found the same local programme on each 
frequency. 

Medium wave stations in the Caribbean are often 
prominent at this time of year. Listen between mid- 
night and OlOOhrs GMT for JBC 750kHz Point 
Galina, Jamaica; ZFY 760kHz Georgetown, Guyana; 
4VEC 830kHz Cap Haitien, Haiti, in French; Radio 
Belize 834kHz in British Honduras; Radio Caribbean 
840kHz in St. Lucia in French; WBMJ 1190kHz San 
Juan, Puerto Rico in English, ZBM1 1235kHz Hamil- 
ton, Bermuda; PJD2 1295kHz St. Martin in Dutch 
and English; Martinique 1310kHz in French. 

Charles Molloy 



1058 



"READ PEOPLE'S MINDS"-TEST THEIR NERVES 
—BEAT THEM AT CARDS— TEST THEIR MEN- 
TAL ABILITY, ETC. WITH THIS ASTONISHING 

ELECTRONIC 
BRAIN-BOX 

li you've eetn a cianf cniitputnr on show at an 
electronics exhibit Inu, you will have seen people 
of ;ill ages queueiug to pit their abilities against 
tlit giant electronic brain- There in j tremendous 
fascination thai attracts ordinary people and 
piofcssional engineers alike i<> electronic games 
01 skill, change anil mystery, wttli this "Brain- 
box" y ou will life able to perform mind-boggling 
tenia. THE MIND READING DEVICE will make 
people xtrtrtr poll hrtrr "tetrpatltic" power*. THE 
AMAZING CARD TRICK UHJT completely 

invsMfi''* an.i IttSta [run. I Iii six people. 

J'riM rorreelly "one**" t/tr t*ro rnrd* each pcrton 
ha* trlertrd at random from a pnvk they them*eU-ri 
*l. u fflr<l. THE ELECTRONICS NERVES TESTER 
puts your friends to a very lively teat U gives out (ail anil llnish signals (the winner is the person 
with lowest ij umber ol Hall siimals.) t.'ini be adjuste** hunt the Khfadtftvlo *fronyegt prrmu. THE ELEC- 
TEOHIC MAZE testt the mental ability nf the ptttyi btmnm St age* psychology wlib ao electronic 
twist to it. You can change the man* pathway? in seconds to prevent the maze becoming too stale 
after lots of use. Couiph-tHy safe ami foolproof. Sign tfi* ■ ia~ X V (Mut.). Vim ean play all these 

fames and more beside filler buildiiie the Itraiii l.n\' ", \VF. ur.MlA.VTEE Til \T AVYONK 
'ROM NIM1-; TO S1SKTV CAN EASILY ASSRJTBLK Aid. THI-MK PROJECTS IS UNDER 
OSE HQl.'Kl You can't go wrong, mi solderiNg, you pat pictorial, ease an a.li.e. step-bv-stcp 
simple instructions. ONLY E2-B7 ($7/S] - 33ji <i;/HI (,.r all parts including ehaxsis, switches, 
stylus. -. hjn u lUng lights, wire. nuts, mm etc. rto, Vtm standard battery. Presentation I3u\ 
3?p (7/6) extra a» ilLut>. K reqd. (PAKTK AVA1I.AIILK SKPAK ATELVl PULL OPERATING 
DIRECTIONS WITH EACH OF THE PROJECTS. 




EAVESDROP ON THE EXCITING 
WORLD OF AIRCRAFT COM- 
MUNICATIONS- JUST OUT 
V.H.F. AIRCRAFT BAND 
CONVERTER 



Hinr thousands ot v.h.i. Aircraft Hand Con vert en now 
selliDE in U.S.A. L4tt** i* to AIRLINES, PRIVATE 
PLAJ.ES, JETPLABES. Kwsdrup vn ex^ffAf rrwif ■! 
bttftwrt jt if 'tis, fftma d itfiprttitch, ground control airport 
fD«rr. /frar far jfourxetf thr ttitctpttned vuirr.% 1,'dinv 
tense net* on talk Aownt. He with them when they have tu 
lake iMM'v-i* lipping tlt-dsinrw in rniergenctafv Tune iuto 
tht- ihicrnatum^ Jjsrtroy* Jjeqin-ncy. Cuvcra the 
aircmfL frniaenci hw\\\ invhiiliiiK HEATHROW* GAT- 
W1CK. LTTTON. RIHGWAY. PRESTWICK ETC., ETC, 
CLEAR AS A SELL. I'M is Isnturtk fully trandstonnrtl 
in^li'iinitiril SOW fcf ^«/ff ty atttjtwr ttfH6 **> tUMtu in undtr 
Hgokovn, {Out- th'^lftn ttium bulH four —everyone worked 
first tiiutt'j. ,V*> k-thwtedQ* ttf radio or rlertronirg r^uirtd. 
Ni. tjutilfi-lGg iu-t?t-<sary » Fully UJu^tratei eimnly wordet] 
ifi.-inii -tiim* Uktf yuii -irp*tiy^tep t t'se* standartl PF^ 
ttatirry, ^iae only 4i* »3'u I J'. All y"o Jo if* extend rt>l 
in 'rial bImm rhi-ir in any orifiuurv tiieiliQrn-wvvp radii" 
u^n, Tim porUblw) MO CONNECTIONS WHAT- 
EVER NEEDED, rat* ind.Kjiy m- ..lildoura. THERE WTLL 
BE ENORMOUS DEMAND FOR THIS NEW DESIGN, 
SEND NOW, ONLY ££37 l47/*lj - 2Sp U/fi) for aJP 
part a. itn:iuiljiitf m«w, miU, aoewi. mire, ate, tfe. fpart^ 
aiai.ithlr ^iian*u-lyf 




£2.37 



AMAZING TRANSISTORIZED 
CIGARETTE RADIO 

Yes. a norlectlr ordlnnrj packet ot cigarettes: Bui watch ymn filonds ^4lnfi-'^^ 
a.stunishineiit on bearing lis range of Htatkms loud and clear. Ilnlds 10 
cigarettes yet conceal™ sensitive, fully tTansMnriscd circuit (including 
tui7 batterj). A yuunu buy can assemble it In iind»r S biur«. So 
solderln*. Only 16 connectione to make. ALL PARTS im-l-idinz 
seitii-conductor". Simple at> ABC IIlusLratCTl Plans, etc. OHLY Slii 
I'iS/fl) + I8p (a/ti) p. * p. Parts available separatclv. 



TOTAL 



£1.47 



C2Sl6t 





ONLY 



SHORTWAVE TRANSISTOR 
RADIO 

Can be built in one evening 

Af last! Alter trying count leas circuits sea retting lor easy build, work 
"J* 6 "! 1 ??* * llort '"«• Giririg advanced world-wide performance, wr chost 
this "Sky Hoina'. Anyone from 9 years up can fallow the stcp-by-.-uep. 
eaHy-an-A DC, (ully illustrated iiwtrmtions, (Wc built ten propotypea and 
every one worked flmt time) no soldering neceKsary. 76 slatiuna logged on 
rod aerial m aO nilnn. —Russia. Allies. tJSA, Switierland, ete. Bxpezionce 
thrills of world wide news, sport, music, etc. Eavesdrop on unusual broad- 
casts. 17m PP3 battery. Transisturiscd inn valve*:). Size only 3* i 4 J' i 1 }-. 
As [reimmiloiiB ileniand anticipated price held to only £8 35 14.3/-) - 
17p 13/B) p. 4 p. for all parts inel. Cabinet, screws, instr. etc. (Part* 
available separately). 



REAL WORKING ELECTRONIC ORGAN 

Dun I nai/uit HilA ordinary electric fryoM thill limply btnv air 

veer mmth-vrgoTi (jfpc rredn etc. Bight uiouths were spent in 

creating ana testing thin superb, revolutionary electronic 

■irgan. Fully «ransistun*ed — no valves. Proper soil-contained 

loudspeaker. Fifteen Me par ale key* I p« n tiro full aetuetn — play 

the "Frtlote tioa o/ Trtat". play "Sil'iit Sight'' , play "Aaid 

Lang Stint", play tnti and lot* of liwilat timet on thla real 

working electronic urgati. AJthouKb ft'i no theatre organ it's 

certainly no tiny thing, 11 measures 13) n 10 * a J", Vmt have 

the thrill ami excitement of building it tugvthi-r "itb the 

pleasure uf playing a real, live, throbbing electronic organ, roie 

it auj/trltrrr -play It angirllrrr, SO PREVIOUS KHOWLEDGE 

OF ELECTROHICS HEEDED— ROME WHATEVER. No 

solder big necessary, it reallv is as simple as a.b.c. to make. 

Anyone Irom nine years upwards can build it easily in one short evening following the fully Illustrated. 

step-by-step, Hiinply winded Instruct i.ais. BIG DEMAND ANTICIPATED FOR THIS URiatlE IHSTRTJ- 

(oo,-> MENT at our low, low building price. OHLY *£-76 (SB/-) -r 38$ i-J/6] p. * p. for all parts, tncludint; 

■as*, loudspeaker, transistors, eondenmrrs, tesialnrs. ItBObs, transformer, vulinoe control, wire, nuts, screws, simple 

tbut fall) instroetions. etc, etc. L ses standard PP;j battery (parts available separatetv). Have ail the pleasure of' making 

it yourself, finish wit ban exciting gdt for i-omeone. 




ONLY 

£2.75 



UNIQUE RADIU FUR BEDROOM OR UFFICE 



No batteries, no electricity, never wears out 



Tune in your favourite programmes or the nuns, or sports lit (lie Ornci- 
or in your bedroom, l/aes sensitive, germanium diode originally evolved 
from Wartime radar. Never buy a battery. Never use electricity. Sever 



ONLY 



replace. Cover* ail uicillum wave*, clear beam I ful tone, size 
4f'i'J(- x IJ- in beautiful ease. OHLY 7 CORRECTIONS 
AHD IT'S WORKING. No soldering necessary. CAN BE 
B01LT ALMOST BLINDFOLD Uf ORDER 15' MINUTES I 
Ideal for absolute beginner from ft years of age upwards. 

[19/SI 
SPECIAL PRICE TO CLEAR STOCKS OF COMPONENTS. ONLY 97n 
(19f6) + I3p (2ffi) p. A p. lor all part> inrlnding beautiful cam- 
tJernianium semiconductor, tDtiiTig ^ondensi^r, personal phone, wir*-, 
nuts, screws. SIMPLE AS A.B.C. INSTRUCTIONS, (Parts available separate! s ,, 

EXAMINE AT HOME FOR 7 DAYS. YOUR MONEY REFUNDED I 

8 

Mr 



97p 



CONCORD ELECTRONICS LTD (Dept. PW18) 




FIND BURIED TREASURE! 

TREASURE LOCATOR 
FULLY TRANSISTORIZED 

NOW IT'S HERE AT LAST, after enperimeutiMr for l'iur and i 

tiatf mouths wiih it multitude of different circuits and carrying 

uiil actual lli-lil li-l- wiTli prololypi-s. our ,lesi^u team hfeVt OBtSmt 

up nith tiiifc (■"»! winner. This fully portable transistorized meul 

local or detiri-la anu tracks down burieit 

metal objects - It signals exact location 

with loud audible sound (nil phones 

useili uses any irausistur rail In which 

FINDS GOLD, SILVER, LOST 

COIRS. JEWELLERY, KEYS. WAR 

SOUVENIRS. ARCHAEOLOGICAL 

PIECES, METALLIC ORE, NUGGETS 

ETC. ETC, Outdoors ur indoors. £>- 

, m,71 sigiutt preiewcr of 

rertattt vbjeets buried several feet br.l">* 

■trnnint' Sit knowledge of nulio m 

■ l,i-l I. .nil'* rei|tilriBl. Can be buitl K*i'lA 

ettir in onr short ewnlntf by anybody 

lno» ii'i>f yeurt of age upward*, with 

Ihe woudrrfully clear, easy lo follow, 

-tep-by-step, fully Illustrate.! 

iTistriicti<uis -it really is easy 

as A, H.c. PuJIy iraiinistoriitil 

no valve.s. Cses siantlard 

PPS battery. N'o soldering 

hi-crssary. Size of dc teeter 

head 131* s III- x a;' 

Great demand expected 

at this remarkabl y lo w 

price ORDER WHILE 

PRESENT STOCKS 

LAST. All purls including 

letector bead ease. nuts. 

'■'i-ira, wire. simple 

■'.* tractions etc, ete 

OHLY £2 37 i47iii) - 

•->3p (47 B) p. * p. 

.Telescopic handle as 

illustrated SI 76 (Ml 

extra). Paii< ava liable 

separately. Jllailc no 

looks worth £1j: 




MAKE 5 PROJECTS 
INCLUDING 3 TRANSISTOR 
LOUDSPEAKER RADIO 




TOTA 
BUILDI 
PRICE 



HI .97 



It9f6l 



^f$&° 



Ai miH Kadi... Construction 
*rt ! lt«:ome a radi" expert for 
£197 139/fi). A t'omplete 
Home ita.li.) t'olirss. .So n 
portosoe needed. Parte Incluii- 
i . ^ s \ i . 1 1 , le iiLsi met i one t or ea*--b 
desiK"- Ilbistrate.l 
~)tep-byslep plans, 
all Transistors, loud- 
s(*eatet. pi-rst.*njil 

phone, knobs, screws, eic. all you need. Presentation Bot 
37p iT/iii I'xtrj as dins, if reipjlre.1 lexlra parts availabk- 
BOtua ■■■H'.-i>i, Send onlj U»7 tasi/ili r ^3p *•*/«> P- « " 
N FULL IF NOT 100% DELIGHTED. 

Westbourne Grove, London W.2. 

Bayswater & Queetuway Tubes. I minute ABC Cinema) 
Callers Welcome 9 a.m. -A p.m. inc. Saturday 



1059 



Fully guaranteed 

Individually packed 

VALVES 



TRANSISTORS, ZENER DIODES etc. 



B12H E175p.ECH84 37p 



CY31 

DAF9B 

DF9B 

DK96 

DL92 

DIM 

_DLS»6 

DM 7(1 

DM71 

DY86 

DY87 

DY8Q2 

F_»«i I y; 

£135p 
E180OC 45p 
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E1B2(X' 

£115 
EABCSO SSp 



WplBOHaw esp 



33p 

sr P 
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EAF42 

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EtX'16'J 

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ECUS I 

ECUS:* 



Ha 



moves 

BCELSi 

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EF38 
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etm 

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lOp | EFL20J. 



EL34 

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£12op 

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31 "p PCWOO 



I'i •)•■.'!] I 
ISp FCF80I 
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25p PCFBOS 
32 ? PI i sort 
35p r PCF8u* 



FCH20II 

pouti 

1V1>2 

pi'i.s;i 
POLH4 
88p;PCL8S 
40p PCL8B 
30p ; PFlaM 
aspipLai; 
sap j pen i 

25p ! PIJW 

40? : PT.l" 

3Sp PL"- 

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35b PX-. 



SPECIAL 
OFFER 

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£1.75 



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Of I it 4Ep 

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1^ 
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top 

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25 [i 



ahm 
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hit:- 
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37p OVBILiAI 20p 
oSp : OC8! Up 



iDr 



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OC200 

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out 

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37j> 
47p 
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sor 
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l.sryu-j-T'jrjsep 

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'2X3054 9Gp 
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2N3730£1-Mp 
■2N3731£l'26p 
2XolOB£2 06p 
40382 67p 
S2303 SOp 
3F100 67p 
3FB5 8BP 
3X128 87p 



series SSp 3X139 £l-75p 



msjOAii 05 

1X823 A £1-30 

12MT5 35p 

IZMT10 "' 

1ZT5 

IZT10 

■241385 

2(1403 

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2NS18 

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2K1307 

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33]i 
B7 5 i 
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55p 

ita 

Hi 

'.lb? 

25p 
2ip 
75p 



;X'2904A 37p 



8/p 2S3053 Efip 



3X140 95p 
3.N154 BOp 
3X159 £l-45p 

•;fr5 • 45p 

12FBIJ0 73p 
IdDI 18 J 

40594 H87P 

40595 £1 37p 
40636 £i 45p 
40683 ll'&Sp 
40663 £l'4Sp 
AC 126 81p 
A CI 27 Zip 
AC1-28 EOp 
AC176 ESp 
AtTi 17 25p 
ACY2H SOp 



65p,g«VO3-10 l-iui 
48p i £1 B5P-6AQ5W" 

42p ;t!4VU.i-40 -(iAgfj 



i';.'ii 



38p EY8I 35p PY33 

77p EY8M 40p PYHO 

82p EZ41 42p PYx 1 

62p EZ80 25p PY82 

80p EZ8I B7PIPY8S 

85pj(JZ34 S2p PYM." 

2Sp K Tiifl £16di|PY8nii 

42p'KT88 £l-75p PY80I 
29«1(t. AERIALS each consisting of ten 311, {iff. die 
tubular scre/.-in sections. 11ft. (6-section) whip aerial 
with adaptor to fit the 7in. rod. insulated base. Slav 
plate and stay assemblies, pegs, reamer, hammer, etc. 
Absolutely brand new and complete ready 10 ereel 
In canvas bag £4. P. &. P. 50p. 

METPRQ Fuil L ' Bt °' our vt,v ' la '8 e 

If 1 1 1 CP.O stock of meters on reauesl. 



£4-2Sp'ijAS7( 

ggvud : 4uA «ATfi 



£5 25p 
1117 40p 

Kill 37p 

!*TV-JM0;40 

£3 00p 
s'l ■\-dnoiil- 

£9 00p 
T'l 



£2-55p 

7Bp 

~2p 

40p 
VAX J" OTBSBM IS 
P. * P. uji tu SOp.'iii: ii 



9AOS 

1IAX4 

rlA\.Mi 

'1117 

lillKT 

tat* 

HBKfi 

i,:i'.iii: 
liltJii 
1IBQ7A 
IIBK7 



(iBWfl 

BBW7 

6C4 

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6CH6 

1J801 



80p 1 UCL83 
B.i p UF41 
28p 1JF80 

20p I'FS9 



ADH'J 


SSp 


BY 21 3 20p 


AD16I 


36p 


BY.Z16 SSp 


AD182 


3Sp 


CKUl/10 EOp 


AF118 


32p 


CKH1/20 87p 


AF127 


17p 


CB91/30 3Bp 


AF139 


3/p 


CBSl/35 4£p 


A WW 


*7p 


CKB1/40 *7p 


AF186 


4fip 


CES13/05 SOp 


AFY19£MEp 


CEH3/20 37 p 


ASY2H 


B7p 


URS-iclii 4Bp 


ASY28 


B7p 


CBH25/025 


ASY67 


47p 


78p 


SAW IM 


87P 


CKS3/40 SOp 


BC107 


lAp 


GET103 BOp 


BC108 


lop 


RET 11.1 45p 


BC113 


30p 


GET 1 HI SOp 


BC118 


37p 


GEX66 76p 


BCY7" 


37 p 


SKT222 EOp 


BF116 


25p 


XKT304 SSp 


BF17S 


30p 


8D91S E8p 


BF187 


GOp 


SD92S 31p 


BFY51 


esp 


en 93S 32p 


BFlf62 


2Sp 


SD94 Elp 


BS05 


87p 


SEE'S S 48p 


BS 


45p 


V40SA 38 p 


BS2 


t«p 


Z Baii£L j 


B8Y2M 


17p 


Zener il hula 


BU100 £1 SOp 


17p t*a 



3V4 40pil2AX7 

6B2S4M £1-80 1 12BA0 

5B/255M 12BE<5 

£175 12 HI 1 7 



ALL valves 
guaranteed 

76p 



5R4GY 

5U4H 

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5Y3GT 

5Z4 

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6AB7 

6AC7 

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6SC7 

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fi3H7 

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12EI 

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aTpii^flA 

30p 1 954 

30p Si 
17p HS'i 
27p 957 
SSp • 991 
SOp ■■ 1622 



19K7GT 33p 21W1 
12K8GT 37p'5933 
70p!12Q7CT S7P'60*">7 
80p : 12S(17 35p «■'"' 
EOp 11487 75pi6064 

16pU9A«0 38p eoas 
57p 19(3 3 £3 SOp 6080 
ESp 10O6 £100p 6146 
32p 19 E4 £4-50p .80211 



6J4VA 

6J5 

6J5GT 

6J6 

SJ7G 

6J7M 
SSp 1 6K6GT 
4Ep 
" 6K7(1 

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6K25 

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VB10Sf3O 80 

VR16(V3080p 



lOp »P4 

BSpiasLWiT 
ISp : 30C10 
SOp!30Cli 
30p 30C18 

65 p son 

Zip i 30FL1 
30p 30FL12 
37p ■ 30FI-1 3 
32p ' 30FL1 I 
3Sp|30L15 



28 p 
43p 

\i? 

55p 
35 p 

75p 
£1 
15p 



5jp L1L41 
£1 UL84 

UABC80 35 p UU5 

L'AF42 62p CY41 

UBC41 47p CY85 

UBF80 35p fiCLB 

1TBF89 SSp 61) 6 

UCC85 40p '6EA8 

UCF80 SOp I BEUT 

CICH42 SBp BF23 

UCH81 SOp ! 6F33 

UCL83 8ap'6H6M 
NTQV/i iitdudr Cath«dc Ray Tubft and Special Vab*i 
£1 Idji: <nej-£l lOp in £1, over £3 pout free. C.O.D. 20p eMra 

INTEGRATiD CIRCUITS— HAMY OTHERS IN STOCK 
RCA. CA 3005 wide band R.F. Ampl. 300mW diss £1-ls 
C A 3012 wide band ampl. 150m W diss .. £ J'1S 

C A 3020 Audio power am pi. ^Jr 7 

C A 3036 Audio pre-ampl Wp 

STC MIC 9301 B Oi glial dual 4 imflut gates .. £4-38 

MIC 709-lC Linear operational ampl 69 

MIC 9005D Highspeed flip-Hop £».?0 

General Electric PA 230 £4-1Z: PA 234 £1; PA 237 £1-87 
Mullard TAA 300 £1-97: TAA 320 S7p 



70p Z75B £l-7op, 6SK 

3Sp ZSO017M-4SP 1 68E7(1T 3Ep 1 30Ll7 

ESp Z80I1" £1 25p 63M7GT 8SPJ30P12 

17p ZS03A £1 25p 63Q7 38p!301*19 



Ht 

•lap 
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32n 
lOp 
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70p 

m 

32 B 



Z900T 

IL4 

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334 



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11E2 £l-60p : 803 
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12AVS £7p!832A 



S7p 
Hi 
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m 

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25= 
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35p 



50C5 
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£1-S0p 

HSU 60p 

75 S7p 

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asp 
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£137p 
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Colomor (Electronics) Ltd. 

170 GOLDHAWK ROAD, LONDON W12. 
Tel: 01-743 0899 
Open 9-12.30, 1.30-5.30 p.m. Thursday 9-1 p.m. 



It costs 



ONLY 63p 



post paid 



900! 

9002 

9003 

9004 

9008 

C.B. Tubes 

VCR 97 

£4S0p 
VCRS17B 

£3 SOp 
VCR517C 

£?B0p 
5F1'7 £l-32p 
8811 £800p 
B3J KBOOp 
88). «9 00p 
Photo Tubes 
CMG26 

£l£5p 
931A fSISp 
6087C 

£X7S0p 
Special Viva 
CV1031 

£5 OOp 
CV2339 

£80-00,, 

25p ! J P9/7D 

4Gp 1 £37S0p 

£3 00plR301 £500p 
aSOOpiKSHA £12-00p 

45p KSOS £16-00p 
£3-75p K337 £1S OOp 
£2-75p) 



&!S8SSS^0 \ for today's MOST USEFUL 

^COMPONENTS CATALOGUE 

Many radio and electronic enthusiasts say that our catalogue is "priceless" ! Be that 
as it may, we charge you only 63 pence. What is more the catalogue contains 6 
vouchers, each worth 5 pence when used as indicated. And for good measure, we 
throw in a useful Bookmark giving electronic abbreviations and a 30-page Price 
Supplement. Why are you waiting? 

By the way, if it suits you to call at our shop you save yourself another 20 pence — 
the post and packing costs. 




POST THIS 
COUPON 

with your cheque 
or P.O. for 63p 



The price of 63p applies only to catalogues purchased by 
customers in the U.K. and to BFPO addresses. 




Please write Name and Address in block capitals. 



Name 

Address 



1rF 



HOME RADIO (Components) LTD. 



Dept. PW, 234-240 London Rd., Mite ham, CR4 3HD 



HD 



1060 



,_. ^ _ _ :;| _ 






:*ij:\v:v:vKx::>:::*x£;; : : : : : : : ^^ 

( ARTHUR DOW 




IN the course of time the average constructor 
accumulates quite a lot of odd small-value 
capacitors which eventually lose their markings 
and identity either by constant handling or by just 
being jostled around in the junk box. In any case 
they are then virtually useless and a positive menace 
and might just as well be thrown away. A lOpF 
capacitor used inadvertently with a tuned circuit 
instead of lOOpF can cause an awful lot of trouble. 

However by using this simple checker these 
capacitors can be rescued and re-marked and an hour 
spent in this way can be very rewarding. 

The usual method of measuring capacity is with 
a bridge using an integral a.f. or r.f. oscillator to 
power the bridge. It occurred to the writer that since 
most constructors have a seldom used 1MHz crystal 
calibrator sitting on the workbench this could be 
put to good use as a signal source for a capacity 
checker. 



In the event the checker proved so useful and was 
used so often that it was decided to integrate the 
oscillator and capacity measuring circuitry. This 
second unit is also described below. 

METHOD 

The usual bridge circuit has not been used. Instead 
a tuned circuit is resonated with the signal source at 
1MHz, the unknown capacitor connected in parallel 
with the circuit and the tuning capacitor reduced in 
value until resonance is restored. 

If the tuning capacity is calibrated (in pF) the 
decrease in its capacity to maintain resonance is 
equal to the value of the unknown capacitor. 

The range of capacity that can be checked is 
approximately equal to the value of the calibrated 
capacitor, in this case up to about 200pF. 

CIRCUIT MK I 

The signal source at 1MHz is fed via a short 
coaxial lead to the input socket Ski, Fig. 1, across 
which is connected the tuned circuit LI, VC1. With 
VC1 at maximum capacity the slug of LI can be 
adjusted until the circuit resonates with the 1MHz 
source. 




Fig. i : Circuit of the Mk t capacitor checker. 



Resonance is indicated by maximum deflection on 
the 50," A f.s.d. meter Ml fed from the rectifier 
circuit Dl and C4 connected across the tuned circuit. 
The f.s.d. of the meter can be adjusted over a wide 
range by the potentiometer VR1 to cater for differing 
input signal levels. 

The capacitor to be measured is connected to the 
terminals Tl and T2. The range can be extended by 
increasing the value of VC1 but the accuracy of the 
read-out will be less, 

SIGNAL SOURCE 

The author had a IMHz-lOOkHz-lOkHz crystal 
calibrator available so this was used originally as a 
signal source for the checker, at 1MHz. There is no 
reason why an ordinary signal generator tuned to 
1MHz should not be used but it should be stable in 
frequency and be fitted with an attenuator or other 
output level control. 

CONSTRUCTION 

All the components are mounted on the lid of a 
small aluminium box 5*4 x 2Vn. and 2in. deep. A 
suggested layout is shown in Fig. 2 (the circuit-board 
and switch SI being ignored), but there is nothing 

1061 



critical in the placement of the few components. 
Care must be taken to ensure that terminal Tl is 
properly insulated from the lid, the two-terminal 
strip specified being fixed to the lid with 6BA bolts 
with a spacing nut between the strip and the fid, the 
wire from Tl being taken through a clearing hole in 
the lid. 







VC1 



Tl 
® 



T2 

® 



Box lid 5jx 



2 5 

^4 



Fig. 2 : Layout of the checker Mk II. In the Mk I version the circuit 
board and switch St are omitted and an input socket ft tied. 



These terminals are spring loaded which consider- 
ably facilitates the gripping of the wire ends of small 
capacitors. 

The inductor LI has its own fixing nut through 
which the slug can be adjusted with a conventional 
hexagonal trimming tool or it may be fixed in posi- 
tion with Araldite. Diode Dl and capacitor C4 are 
wired directly between components. 

A stiff white cardboard dial, 2 1 2in. diameter, is 
clamped underneath the retaining nut of VC1. A thin 
perspex pointer with a hairline scribed on it is stuck 
to the underside of the knob on VC1. 

CALIBRATION 

After checking the wiring, such as it is, set VC1 to 
maximum capacity and adjust the pointer to the zero 
fine on the dial. Feed in a signal at 1MHz from the 
crystal calibrator and adjust VR1 for a reasonable 
deflection on the meter. 

Adjust the slug in LI for a peak on the meter 
reducing the signal input or increasing VR1 until the 

1062 



* components list 




Resistors : 

R1 220k «iW 

Capacitors : 

C1 1000pF SM 

C2 820 pF SM 



R2 1kiUW 



VR1 470k pot. 
(miniature) 



C3 
C4 



22pFSM 
O.OIjuF disc 



VC1 200pF variable (Jackson Type 87/057) 

Semiconductors : 

Trl AF117 D1 OA91 

Miscellaneous: 

X1 1MHz crystal, type HC6U and holder (Henrys) 
L1 Inductor, HQ4 (Electronic Techniques (Anglia) 

Ltd., Viking Works, Kirton, Ipswich, Suffolk. 
M1 Meter, 50/iA f.s.d. (Henrys Type MRA38) 
Battery 9V, (PP3) and connectors 
Terminals, black and red (Henrys SLT2) 
Piece of Veroboard. Knobs. Miniature on/off switch 
Aluminium box 5£x2$x2in. (H.L. Smith) or similar 



peak deflection coincides with the f.s.d. 

Using a series of capacitors of known value, prefer- 
ably of 1% tolerance, connect each in turn across the 
terminals. When this is done the meter reading will 
drop as the tuned circuit is no longer resonant at 
1MHz but it may be peaked again by reducing VC1 
at which point the scale should be marked with the 
value of the known capacitor. Some constructors may 
wish to use the preferred range of values such as 
22, 47, 68pF etc., when calibrating the dial. 

In use VC1 is set to zero on the dial and VR1 
adjusted for full scale deflection. The unknown 
capacitor is connected to the terminals and VC1 
rotated to restore full scale deflection on the meter. 
The dial reading at this. point being the value of the 
capacitor under test. 

If, with the unknown capacitor in circuit, it is 
found that it is not possible to regain f.s.d. it is likely 
that the capacitor insulation is down although it may 
still be of the order of megohms. 

CIRCUIT MK If 

In view of the great use to which the checker was 
put it was decided to integrate the I MHz oscillator 
and the capacity measuring circuitry to obviate the 
necessity of connecting the two units together every 
time a capacitor was to be checked. 

The original crystal calibrator was a valved job so 




— continued on page 11 



HARVERSONIC SUPER SOUND 
10 + 10 STEREO AMPLIFIER KIT 




HEW IMPROVED MODEL with hi GHEE OUT- 
POT AND INCORPORATING HIGH QUALITY 
HEADY DEHLED PRINTED CIRCUIT BOARD FOE 
EAST CONSTRUCTION 



A really first-class Hi-Fi Stereo Amplifier Kit. Uses 14 
transistors including Silicon Transistors In the first five 
stages on each channel resulting In even lower noise 
level with Improved sensitivity. Integrated pre-amp with 
Baas, Treble and two Volume Controls, Suitable lor use 
with Ceramic or Crystal cartridges. Output stage for any 
speakers from 5 to 15 ohms. Compact design, all parts 
supplied including drilled metal work, high quality 
ready drilled printed circuit board, attractive front panel, 
knobs, wire, solder, nuts, bolts — no extras to buy. 
Simple step by step Instructions enable any constructor 
to build an amplifier to be proud of. Brief specification; 
Power output : 14 watts r.m.a. per channel into B ohms. 
Frequency response ±3dB 12-30,009 Hs Sensitivity: 
better than 80mV into 1MQ. Full power bandwidth: 
±3dB 12-18,000 Hi. Baas boost appro*, to ±12dB. 
Treble cut approx. to - 16dB. Negative feedback ISdB 
over main amp. Power requirements 35v. at 1.0 amp. 
Overall Size 12'w. x S'd. X 2|'h. 

■Fully detailed 7 page construction manual and parts 
list free with kit or send I8p plus large 8.A.E. 
PRICES 

AMPLIFIER KIT , . . . £10-60 P, ft P. 15p 

POWER PACK KIT .. *3-00 P. & P. 25p 

CABINET £8-00 P. A P. 25p 

(Poet Free if all units purchased at same time) 
Full after sales service 
Also available ready built and tested ££0-50. Post Free. 
XoU: The above amplifier is tuilablt for feeding two mono 
sources into input t {e.g. mike, radio, twin record dtcki, tie.) 
and mill litem provide mtxtnn and fading facUiliei for med- 
ium powered II i Fi Dltcothegue use, etc. 



FANTASTIC 'POLY PLANAR' WAFEB-TYFE, 

WIDE RANGE ELE0TEODYNAMIC SPEAKER 
Siieouly 11 1" x 14 ji* x 1 A" deep. Weight only lOozs. 
Can replace cone speakers In any application and is 
particularly useful for those with limited space. 
Extremely rugged and shockproof. Operating 
temperature-— 20°F to 175°F, Power handling 10 
watts rms (20 watts peak). Impedance 8 ohm only. 
Response 40 H s - 20 K 11 z . Can be mounted o u ce 11 lugs, 
walls, doors, under tables etc. and used with or 
without baffle. Send S.A.E. for full details. ONLY 
£8.76 each. P. ft P. 23 p 



MAGKAYOX DESK TYPE MOVING COIL MICROPHONE. 

Medium imp. Brand Sew. Special Price £2-10 p. ft p. lOp 

SINGLE HEADPHONE". With aluminium headband. 

Approx. 200 ohm, SSSp. P. A P. Sp 

CRYSTAL MIKES. High imp. for desk or hand use. 

High leniltivitv, 93p. V, ft P. 8p 

HIGH IMPEDANCE CRYSTAL STICK MIKES. 

OCR PRICE £1-05. P. * P. 8p 

HIGH IMPEDANCE DYNAMIC STICK MIKES. 

High sensitivity. £1 -°8. P. ft P. 13p 

PIASO KEY TYPE SWITCHES. 8 press buttons plus 
1 cancel button. Each of the 8 sections contains 8 s.p.c.o. 
(total 48 s.p.c.o.). Brand new — limited quantity only. 
Original manufacturing cost £l-37£. OCR PEICE 75p. 
P. ft P. 13p [3 nr more unfit f ree). 

HONEYWELL MICE OS WITCHES, Sit. 0/0. Push button 
action. Hating 2B0v, AC at 15 amps. Slie approx. 
It -* j X fin. 25 P earll. I'. * P. 3p i'6 nr mure post tree], 
SPECIAL OFFER; PLESSEY TYPE 28 TWIN TDTfiNG 
GANG. 400pF + 146pF. Fitted with trimmers and 
6:1 integral slow motion. Suitable for nominal 470 k/se 
I.F. Siae appox. 2x1x1,. Only 43p P. ft P. 13p. 

TELESCOPIC AERIALS WITH SWIVEL JOINT, Can 
be angled and rotated In any direction. 6 section Lacquered 
BrasB. Extends from Din. to 22 ? in, approx. Maximum 
diameter j-in. gSp each. P, ft P. Sp. 



SPECIAL OFFER ! 

HI-FI LOUDSPEAKER SYSTEMS 

BeautlluUv made teak finish enclosure with most 
attractive Tygan-Uynair front. Size 161* high x 10,' 
wide x Sf* deep. Fitter with E.M.I. Ceramic Magnet 
13* x 8' bass unit, two H.F. tweeter units and 
crossover. Power handling 10 watte. Available 3 or 
8 or 15 ohms impedance. 

OUR PRICE £8.40 c&rr.so P 

Also available in 8 ohms with EMI 13* x 8' bass 
speaker with parasitic tweeter 16-60 Carr. 5 Op 



LOUDSPEAKER BARGAINS 
3* 4 ohm OOp. P. ft P. 8p. Bin. S ohm 80s, P. * P. 15p. 
7 X 4to, 3 ohm il-0S, P. ft P. 20p. 10 x 6in. 3 or 15 ohm 
£1-80, P. A P. 30p, E.M.I. 8 x 5ln. S ohm with high 
flux magnet *1-«B. P. ft. P. 20p E.M.I. 13j x8ln. 3 ohm 
with high flux ceramic magnet £2-10 (15 ohm *2-26). P. ft 
P. 30p. E.M.I. 13 x Sin. 3, 8 or IB ohm with two Inbuilt 
tweeters and crossover network £4-20, P. 4 P. 30p. 
E.M.I. IS' x 8' twin cone (parastatic tweeter) 8 ohm 
£2.25 p ft P 30p. 

BRAND NEW. ISm. I5w, H/D Speakere, 3 or 16 ohms. 
Current production b y well-known British maker. Now 
with Hlflux ceramic ferrobar magnet assembly £5-50. 
P. A P. 38p Guitar models: 2 a w. IS -50, 35 w, £8-50. 
E.M.I. 3 tin. HEAVY DUTY TWEETERS. Powerful 
ceramic magnet. Available In 3 or 8 or 15 ohms 68p 
each. P. ft P. I3p. 

18tn. "RA" TWIN CONE LOUDSPEAKER. 10 watts 
peak handling, 3 or IB ohm 11 ■88. P. ft P. 30p. 
85 OHM SPEAKERS 3in. 70p, P. ft P. 13p. 



HI-FI STEREO HEADPHONES 

Adjustable headband with comfortable SexJfoam ear- 
muffs. Wired and fitted with standard stereo Jin jack 
plug. Frequency response BO-lfi.OOOHz. Matching 
impedance S-1S ohms. PRICE £B-B5. P. ft P. 15p- 



OENERAL PURPOSE HIGH STABILITY 
TEAHSISTOR PEE-AMPLIFLEE 
For P.U. Tape, Mike, Guitar, etc. and suitable for 
use with valve or transistor equipment. 9-lBv. 
battery or from H.T. line 2OO/3O0V. Frequency 
response 15 Hi— 25 K Hi. Gain 26dB. Solid encap- 
sulation siie II" ill'i 1". Brand new complete 
with instructions. Price B8p. P, ft P. 13p. 



BRAND HEW MULTI-RATIO MAMS rBANSFOH- 
MEBS. Giving 13 alternatives. Primary: 0-210-240V. 
Secondary combinations 0-5-10-15-20-25-30-35-40-«Ov, 
half wave at 1 amp. or 10-0-10, 20-0-20, 30-0-30v, at 
2 amps Cull wave. Bile 3ln. long X 3iin. wide x 31n. deep. 
Price 11-76 P. ft P. Slip. 

MAINS TRANSFORMER. For transistor power supplies, 
Prl 200/240v. See. 0-0-9 at 500mA. 70p. P. ft P. lap. 
Prl. 200/240V. Sec. 12-0-12 at 1 amp. 88p. P, ft P. 13p. 
Prl. 200/240v. Sec. 10-0-10 at 2 amp. il-88. P. A P. 18p. 
Tapped Primary 200-220-240v. Sec. 21.5v. at 500mA. 
08p. P, ft P. 13p. 

BATTERY CHARGER TRANSFORMERS. 200/240r. in- 
put. Nominal output for 6 or 12v. batteries 3 amps. Size 
approx. 3-x2J"x2i\ Brand New. Price £1-05. P. ft F. 25p, 



BRAND NEW EJC.I. LIGHTWEIGHT PICK-UP ARM 
WITH ARM REST, Pitted mono t'o stylus and cartridge 
lor LP/78. ONLY £1, P. ft P. 13p. 

QUALITY RECORD PLAYER AMPLIFIER MK H 

A top quality record player amplifier employing heavy 
duty double wound mains transformer, ECCB3, ELS4, 
and rectifier. Separate Bass, Treble and Volume controls. 
Complete with output transformer matched for 3 ohm 
speaker. Site Tin. wide x 31o. deep x 8in. high. Ready 
built and tested. PRICE £8-76 P. ft P. 30p 
ALSO AVAILABLE mounted on board with output 
transformer and speaker ready to fit into cabinet below. 

FKICG £*-88 P. ft P. 38p. _^ _-, -- 

DELUXE QUALITY PORTABLE R/P CABINET MX H. 
Uncut motor board size 14} x 12in, clearance 21n. below, 
Blin above. Will take above amplifier and any B.S.S. or 
GARRABD changer or Single rlayer (except AT60 and 
SPSS), Size 18 x IB x Sin, PRICE £8-88. P. ft P. 4SP- 



10/14 WATT H 

A stylishly finished 
monaural amplifier 
with an output of 
14 watts from 2 
EL84s In push-pull. 
Super reproduction 
of both music and 
speech, with negli- 
gible bum. Separate 
inputs for mike and 
gram allow records 
and announcements 
to follow each other . 
Fully shrouded section wound" output transformer to 
match 3-16 Q speaker and 2 independent volume controls, 
and separate base and treble controls are provided 
giving good lift and cat. Vadve line-up 2 El&to. ECC83, 
EF80 and EZS0 rectifier. Simple instruction booklet 
13p (Free with parts). AH parts sold separately. ONLY 
£7-97 P. ft P. 43p. Also available ready built and tested 
complete with atd. input sockets, £9 -97. V. ft P. 43p. 




BRAND NEW TRANSISTOR BARGAINS. GET 15 
(Matched pair) 75p; V15/10p 60p; OC71 S6o; OC76 
80p: AI-'117 18p; 2G339 (NPN) 15p. 
Set of Muliard 6 transistors OC44. 2— OC45, AC128D 
matched pair AC128 tl2S: ORP12 Cadmium Sulphide 
Cells S3p. All post tree. ^^^^ 



VERY POWERFUL COMPACT MOTOR 

For 12v, D.C. operation. OfT load consumption approx. 
100mA. Totally enclosed. Quiet in operation with high 
starting torque. Overall size approx, 1J"L x 11' dia. 
Free shaft A " dia. x ,*L. Ideal for Model Makers, etc. 
ONLY SSp- each P. ft P. Sp. 
3 or more post free <A few flv. versions also available) 



HIGH GEADE COPPEB LAMINATE BOARDS, 
8 x 6 x Ain. PTVB for SOp. P. ft P. 10p- 



DE LUXE STEREO AMPLIFIER A amain. 

200-240 t. 
Using 
heavy duty 
fully isola- 
ted mains 
transform- 
er with full 
wave recti- 
1 1 e a 1 1 o n 
giving ade- 
quate 
smoothing 
with negli- 
gible hum. 

valve line up: — 2 x ECLae Triode Pentodes. I X E£80 
as full wave rectifier. Two dual poteutionmeters are 
provided far bass and treble control, giving base and 
treble boost and cut. A dual volume control Is used. 
Balance of the left and right hand channels can h* 
adjusted by meana of a separate 'Balance* control fitted 
at the rear of the chassis. Input sensitivity is approxi- 
mately 300m/ v for full peak output of 4 watts per channel 
(8 watts mono), into 3 ohm speakers. Full negative 
feedback In a carefully calculated circuit, allows high 
volume levels to be used with negligible distortion. 
Supplied complete with knobs, chassis size ll"w x 4"d. 
Overall height Including valves 5". Ready built and tested 
to a high standard. PRICE £8 96 F. ft P. 40p. 




a nign stam 
4-&EED 



RECORD FLAYER, BARGAINS 

Maim models. All brand new In maker's packing. 

LATEST B.S.R. ClCrB/ASl 4-SPEED ADTOCHASGES. 

With latest mono compatible cartridge (6-87 Carr. 38p. 

With stereo cartridge £7 -87 Carr. SSp. 

SUITABLE PLINTH UNIT FOR ABOVE with rigid plastic 

cover. £6-76 complete P. ft P. 43p. 

LATEST GARRARD MODELS. All types available 1025, 

£025, SPSS, 3000, ATS0 etc. S.A.E. for latest Prices! 

PLINTH UNITS cut out for Garrard Models, 102S, 2026, 

2000, 3OO0, 3500 etc. With rigid transparent plastic cover. 

Special design enables above models to be used with cover 

in position. Also suitable for housing ATBO and BP25, 

OUR PRICE 1S.76 complete. P. ft P. 43p. 

LATOf Aco'd GPSl/isC rnono compatible cartridge wilh 

t/o stylus [or LP/EP/78. Universal mounting bracket. 

£1-50 P. ft P. Sp. 

AC OS HI-G Single sided mono cartridge for LP ft EP. 

ONLY 5Xh>. Post Free. 

SONOTOBE 9TAHC COMPATIBLE STEREO C AETRIDO E 

T/O stvlns Diamond Stereo LP and Sapphire 78. 

ONLY *2-S0 F. 4 P. lOp. 

Also available fitted with twin Diamond T/O stylus for 

Stereo LP. ONLY £3. P. ft P. lOp. 

LATEST RONETTE T/O STEREO/COMPATIBLE 
CARTRIDGE for EP/LF/8tereo/78. £1-68 P. ft P. 10p. 
LATEST RONETTE T/O MONO COMPATIBLE CART- 
RIDGE for playing EP/LP/78 mono or stereo records 

on mono equipment. Onl y £1-M P. ft P. lOp, 

HJGrT GAtN 4 TRlksisTOE 

PRINTED CIRCUIT 
AMPLIFIER KIT 
TypeTAl 
Peak output 
in excess of 
li watts. All 
stand a r u 
British eom- 
p o n en tt. 
Built on 
printed cir- 
cuit panel 

sixe 6 x Sin. Generous size Driver and Output Trans- 
formers. Output transformer tapped for 3 ohm and IB ohm 
speakers. Transistors (GET1U or 81 Muliard AC12SR 
and matched pair of AC 128 o/p). 8 volt operation. 
Everything supplied, wire, battery clips, solder, etc. 
Comprehensive easy to follow Instructions and circuit 
diagram 13p (Free with Kit). All parts sold separately. 
SPECIAL PRICE £2-48 P, ft P. 15p. 
AIpo ready built and tested. £ 2-75. P. ft P- 15p. 

s-TAIve AUDio 

AMPLIFIER HA34 MK II. 
Designed for HI-FI reproduc- 
tion of records. A.C. Mains 
operation. Ready built on 
plated heavy gauge metal 
chassis, slxe 7 1* w. x 4" d. x 
4J" h. Incorporates ECC83, 
EL84, EZ80 valves. Heavy 
duty, double wound mains 
transformer and output trans- 
former matched for 3 ohm 
speaker. Separate volume control and now with improved 
wide range tone controls giving bass and treble lift and 
cut. Negative feedback line. Output 4f watts. Front 
panel can be detached and leads extended for remote 
mounting of controls. Complete with knobs, valves, etc., 
wired and tested for only £4-75. P. ft P. 30p. 
HSL "FOUE" AMPLIFIER KIT. Similar in appearance 
to HA 34 above but employs entirely different and 
advanced circuitry. Complete set of parts, etc, 13-88. 
P. Hi P. 30p. 

HARVKBSOH'S SUPER MONO AMPLIFIER 

A super quality gram amplifier using a double wound fully 
isolated mains transformer, rectifier and ECLS2 triode 
pentode valve as audio amplifier and power output 
stage. Impedance 3 ohms. Output approx. 3.5 watts. 
Volume and tone controls. Chassis size only Tin, wldt 
x 3in. deep x Sin. high overall. AC mains 200/240v. 
Supplied absolutely Brand New completely wired and 
tested with good quality output transformer. 
FEW ONLY. £2 75 F- 





BARGAIN PRICE 



30p 



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Saturday 

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1063 













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26 


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S01 E 1,34 


63 N7S 


£115 PLE04 


80 1 U404 


40 




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30 


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86 


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58 


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88 


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83 UAF42 


65 






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40 


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66 7R7 


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85 


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60 




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46 


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38 EL 95 


35 


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60 


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46 




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60 20P4 


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85 


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30 , ELLS0 


£100 


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80 PY33 


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40 




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83 1 SBWfi 


60 20P5 


ta-M 


7^ 45 


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20 


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90 


PC97 


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30 UBFS9 


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40IPYS2 


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68 


PCXJ89 


58 


PY83 


38 


UCC86 


40 




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33 ! HKRGT 


60 


10i'» 


90|2SY3 


80 


150B2 60JDH77 


30 


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60 


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88 


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65 


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£1-00 


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66 




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38 


(',( :«i : 


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76 


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53 1 £584 


83 


160C4 60 


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40 


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70 


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34 


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60 


UCH42 


70 




186 


2S 


ecB 


85 1 6L6G 


40 


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45 1 3SZ6 


56 


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86 


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66 


807 60 


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43 


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35 


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60 


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SO 


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38 




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35 


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55 6Q7G 


30 


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68 ' 30<?1 


34 


813USA£6-00 


DKB6 


48 


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40 


EZ40 


45 


PCF86 


60 


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40 


UCL83 


60 




3Q4 


40 


6CW4 


88 SQ7GT 


43 


11 E3 


£4-00 30C15 


80 


see a 75 


DL88 £1-86 


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35 


EZ41 


48 


PCF801 


60 


8130 


£2.00 


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60 




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46 


6Dfi 


86 6SA7M 


40 


12AT8 


30 30C17 


85 


954 SO 


DL92 


86 


ECL83 


66 


E280 


K 


PCF802 


60 


SF4 


40 


TJF89 


38 




tH 


35 


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38 6SC7 


35 


12AT7 


33 30C18 


75 


1623 40 


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35 


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46 


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28 


PCF8M 


75 


8P41 


45 


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70 


6SG7 


30 


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30 30 FJ 


86 


4022AR £5-00 


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76 


PCF806 


70 


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55 


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36 




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80 


8F5G 


50 


6SH7 


18 


12AU7 


30 30FL1 


76 


5763 70 


DL9S 


40 




*l-75 


GZ30 


50 


POPS OS 


78 


8TV280/8O 


E"M80 


88 




OU4G 


S3 


8F6G 


30 


6SJ7 


30 


12AX7 


38 30FL1-J 


85 


71B3 80 


DL96 


48 


EF9 


£1-00 


GZ32 


50 


PCL82 


39 




£4-75 


PXT6 


81*06 




5V4G 


P 


6F8CS 


35 


6SK7GT 


30 


12BA6 


35 : 30FL14 


78 


7475 70 


DM70 


30 


EF37A 


SO 


G234 


60 


PCL83 


86 


8U25 


B8 


t*lf7 


£1<0S 




SY3GT 


33 


8F11 


38 


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35 


12BE8 


35 


30L15 


86 


A61 48 


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38 


EF3S 


40 


ET36 


£1-00 


PCJj84 


43 


Bi;*2150 


75 


DUB 


£1>05 




SZ4G 


40 


6F13 


38 


6SS7GT 


ys 


19CSOX 


86 


30L17 


85 


ATP4 36 


DY87 


86 


EF41 


85 


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11-86 


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£1-35 


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£1-13 


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65 


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25 


KT69 


*l-"0 PCL86 


46 1 TDD4 


43 


UY21 


48 




SAT 


75 


SPSS 


80 


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W 


12J5GT 


86 


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96 


ATP7 60 


EA50 


80 


EK80 


25 


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£1-75 PDSOO 


E1-50ITH41 


£1-76 


UY41 


45 




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63 


8F24 


75 


6L*5G 


39 


12J7GT 


45 


aopia 


80 


AU2 £4.00 


EABCSO 


36 


EF8S 


35 


KT8K7C5) 


PENA4 61-00 U 10 


60 


TTYSS 


38 




SAKS 


tt 


8 KM 


75 


6V6M 


SO 


12K7GT 


36 


SOP LI 


80 


ACS 60 


EAF42 


35 


EF86 


30 




£1-13 


PE>B4 £1-001 U14 


SO 


V3LP4G 


86 




'» A M -> 


38 


6F28 


70 


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83 12K8GT 


60 


30PL13 


88 


AZ1 48 


EBS1 


80 


EF8B 


28 


ET8S 


£1.75 


PEN45 


40 via 


tS -50 


YP4B 


fj.95 




6 ami; 


33 


6F32 


85 


6V6GT 


88 1 12Q7GT 


35 


SOP LI 4 


80 


AZ31 55 


EBC33 


60 


EFB1 


38 


KTWB181-00 


PEN46 


40 T26 


78 


VB 105/30 38 




8AQ5 


35 


BG8 


85 


8X4 


30J128A7 


40 


;■;:■. \„ 


76 CBL31 80 


EBC41 


63 


EFB2 


40 


KTZ41 


45 


PLB8 


65 088 


78 


VRJ 30/3(1 85 




8AS7G 


80 


8E8 


15 


6X5 G 


86 12SG7 


30 


SOLO 


45 CCH35 75 


EBC90 


30 


EF08 


75 


M1.4 


88 


PE81 


50 U78 


30 


YU111 


80 




8AT6 


80 


&J5M 


60 


6X50 X 


3i 


128H7 


rr 3SW4 

15 35Z3 


30 


CL33 £1-00 


EBF80 


40 


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33 


MI.fe 


40 


PLS2 


M 0191 


75 


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80 




8AU8 


86 




60 


CV4S0 £l-86 


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45 


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36 


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60 


PL63 


46 U2S1 


82 


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12-50 




6B4<3 £1.001 wow 


80 


7B6 


70 


123 J 7 


80 j 35Z4G1 


50 


CY30 68 


EBF89 


33 


EL82 


30 MU14 


80 


PL84 


40 II 301 


S3 


TVS1M 


88 




filMR 


SOISJSOT 


80 7B 


45 128K7 


26 1 :;,.X,. 


30 


CY31 48 


EBL1 


70'EL33 


S8MX40 


63 PL300 


B0]U4O3 


50 Yfi3 


38 




New Transistors II 


40 254289 
45 AAZ12 


20 Alll-iu 

30 AD149 


80 BC169C 15 
50 BF898 88 


GET882 
GJ7M 


30 
38 


NET223 

NKT251 


S3JOC.5S 
86(OGI4 


80 


OC8LD 

OC32 


80JOAZ200 
26 (» \Z2fil 


55 
60 


Z8170 
Z9271 


IS 
18 








2S2369A 


HIaoim 


25 AP HI 1 


38 BFY50 26 


K8100A 


SO 


NKT713 


25.0C45 


80 


OC82D 


15' t).iZ-.*l.'7 


48 


ZTX107 


16 




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08!-i>-Btt7 


M 252646 


60 ACI27 


86 AF113 


30 BF"i51 80 


HJE520 


88 


OA70 


10 OC57 


60 


OC84 


86 OAZ210 


83 


ZTK108 


16 




1S113 


35I-2N70G 


15 252904 


80 AC128 


85 API 17 


86 BY100 20 


MJE2935 




OA71 


20 OC58 


SO 


OC170 


25 OAZ222 


40 


ZTX300 


16 




18909 


mzmis-i 


45 252926 


IS ACY20 


23 BC107 


15 j BZY88 Series 


£1-75 


OA81 


XOlOCjB 


M 


OC171 


80 OAZ224 


38 


ZTX304 


81 




2O302 


23 2SL305 


85 S53055 


75 ACY39 


55 BC10B 


15 CES1-40 48 


UJE305S 


93 


OA86 


18 OC71 


15 


OC200 


38 OAZ241 


23 


ZTX500 


16 




2G371 


8313^^1 47 


75 253702 


15 ASY26 


25 BCtOB 


20 DD003 15 


NKT212 


27 


OA91 


10 OC72 


25 


OCP71 


98 OAZ242 


83 


ZTX503 


SO 




2N404 


Ba!2N!>100 81.86 l 2N3aiB 


35 


1 


|GET102 30 


NKT214 


16 


OA2H 


40 1 OC> 1 


26 


OBP12 


60|OAZ240 


23 


ZTX531 


30 










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The New PlCture-B00k way of learning 

O A tClsf* ELECTRICITV(5vols) 
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PICTORIAL APPROACH to learning is the 
quickest and soundest way of gaining mastery 
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TO TRY IT, IS TO PROVE IT 



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"TERRIFIC TECHNICAL EDUCATIONAL 
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A TECH-PRESS PUBLICATION 

1064 




I—RICHARD COLLINS 




THIS simply constructed crystal tuner has many 
advantages to offer. It is easy to construct, 
compact and does not require any power 
source. 

In this article the construction of a crystal diode 
tuner is described. It can be used to provide a signal 
that can be fed into a tape recorder, amplifier, or 
just a pair of high impedance headphones, so be- 
coming a simple crystal receiver. Full constructional 
details are given so that a complete beginner may 
build the project. 

The layout of the tuner is by no means critical 
and constructors can position the components to 
suit the box in which the unit is to be built. 

The prototype was constructed in a small plastic 
case obtained from one of the advertisers in this 
magazine but any small box of similar size, be it 
made from plastic, metal, wood, etc., is suitable. 




Fig. f : Circuit of the crystal tuner, A resistor R1, 10kQ, should be 
shown across the 001 uF capacitor, but see text. 

The complete circuit is shown in Fig.l and from 
this it can be seen that very few components are 
employed; a coil, trimmer capacitor slightly modified, 
diode and resistor together with an aerial socket 
and the "business" end of a jack plug. The use of 
a jack plug helps to eliminate any losses of signal 
strength and reduces any hum that may occur. 

There are only three holes to make in the case 
and the sizes of these are determined by the par- 
ticular types and makes of components employed. 
One of these is for the aerial socket, one for the 
tuning capacitor and the third for the jack plug. The 
coil may be either glued to the casing or held in its 
position by employing fairly thick wire for con- 
necting (bell wire from Woolworths will be ideal for 
this). 

Before construction begins, the tuning capacitor 
or trimmer VC1 must be modified somewhat so that 
it can be used with a knob. 

As can be seen from Fig. 2b, the original bolt has 



been removed and a longer bolt inserted, (a lin. 6BA 
round-headed bolt will do). This should be screwed 
through the trimmer from the back. The trimmer 
should then be set in the "open" position and the 
end of the bolt snipped off so that about Mb. is left 
for fixing the "knob." This knob shown in the proto- 
type was a small perfume bottle cap with a nut glued 
inside it. When the glue had set, a small amount of 
glue was spread onto the thread of the nut. After a 
while, the knob was screwed onto the thread and a 
good solid fixture was made. This knob can be fabri- 
cated from the lid of an old toothpaste tube or any- 
thing of similar size. 

When the trimmer capacitor has been modified, 
a hole of suitable size should be drilled in one end 
of the case as shown in Fig. 3. Should constructors 
wish, they can use a small 500pF variable capacitor — 
the size being dependent on the size of case em- 



Bolt head- 




2^ 



Ordinary bolt 




6BA 
nut 



Knob glued on 



(a) (b) 

Fig. 2 : Tuning capacitor modification. 

ployed. Another hole to fit the aerial socket through 
should be drilled in a suitable position (if the case is 
made of metal, this socket should be of the insulated 
lead-through type). 

The third hole, for the jack plug, should then be 
made. This, being the largest is best started off with 
a hot soldering iron in the case of plastic or wood 
(a drill and file are best used to make a neat job in 
a metal box). 

If this hole is made slightly smaller than the thread 
on the shank of the jack plug, it can be screwed 
into the actual case for a tight fit rather than have a 
securing nut fitted. This is a preferred way of mount- 
ing as a securing nut may foul the jack connecting 
tags. 




Fig, 3 : Component layout and wiring diagram. 

The three items may then be fitted in their respec- 
tive positions (see Fig. 3) and the wiring commenced. 

The coil, a Repanco DR.X1 employed in the proto- 
type was a medium /long wave component but only 
the medium wave winding was connected. A piece 
of wire should be taken and connected to the blue 
and red tags on the coil LI. This wire should then 

1065 



be taken to one of the tags on the trimmer capacitor 
VC1, Another wire should be taken from the other 
tag of VC1 to the black tag on the coil. From the 
blue and red connections on the coil, a wire should 
be taken to the centre connection on the jack plug. 
Resistor, Rl should be connected across the centre 
tag and the other tag and the black end of the 
crystal diode should be connected also. The positive 
or red end of the diode should then be connected to 
the aerial socket. A wire should then be taken from 
this to the tag on the capacitor VC1 that goes to 
the black tag on the coil. Some constructors may 
wish to employ the long-wave winding on this coil 
and if this is so, a suitable on/off type switch may be 
mounted in any convenient position in the case. The 
tuner may now be tested and an aerial should be 
plugged into the socket and the jack plug connected 
to an amplifier input. Wires may be secured with 
Sellotape while testing takes place. When the tuning 
capacitor VC1 is rotated, a station should be heard. 
If two stations are heard simultaneously, a capacitor 
about 100 pF value should be inserted between the 
aerial and the aerial socket — this should help separa- 
tion. 

It has always been the author's policy that the best 
aerial is one that has as much wire up as high as 
possible and this is certainly the case as far as crystal 
receivers go. A length of wire between 50-1 00ft. 
should suffice. 

If it is wished to build up this circuit just for use 
as a crystal set, the lOkffc resistor may be omitted. ■ 



PRACTICAL WIRELESS 

QUERY SERVICE 

Before using the query service it is important to read the 
following notes: 

The PW Query Service is designed primarily to answer queries on 
articles published in the magazine and to deal with problems which 
cannot easily be solved by reference to standard textbooks. In 
order to prevent unnecessary disappointment, prospective users of 
the service should note that: 

(o) We cannot undertake to design equipment or to supply wiring 
diagrams or circuits, to individual requirements. 

(b) We cannot undertake to supply detailed information for 
converting war surplus equipment, or to supply circuitry. 

(c) It Is usually impossible to supply information on imported 
domestic equipment owing to the lack of details available. 

(d) We regret we are unable to answer technical queries over the 
telephone. 

(e) It helps us if queries are clear and concise. 

(I ) We cannot guarantee to answer any query not accom- 
panied by the current query coupon and a stamped addressed 
envelope. 





QUERY COUPON 




This 


coupon is available until 8th Apri 


and 


must 


accompany all queries in accordance wi 


th the 


rules 


of our Query Service. 




— 


PRACTICAL WIRELESS, APRIL 1971 








PLUG-IN TUNER— cant ined from page 1062 

it was thought better this time to employ a transistor 
oscillator and to put it and the battery supply in the 
orginal box with the tuned circuit etc. 

This version of the checker is therefore ready for 
instant use. 




Fig. 3: Circuit Mk fl incorporating a 1MHz oscillator signal source 



The oscillator is straightforward and uses an 
AF117 p.n.p. germanium transistor and an HC6U 
style 1MHz crystal unit, Fig. 3, and is constructed 
on a small piece of Veroboard, Fig. 4. The board is 
mounted between the meter and the tuning capacitor 
VC1 by a stiff copper wire soldered to the earth side 
of VC1, as can be seen in the photograph. 

The output of the oscillator is connected to the 
.original tuned circuit by C3. 

The method of measuring the value of an unknown 
capacitor is the same as before except that initially 
the step of adjusting the core of LI should be 
repeated since the permanent capacity across the 
tuned circuit will now be different. 



XI Holder 



Stiff copper wire 




Fig. 4: Circuit board of the 1MHz oscillator buiit on Veroboard, 0-15 
x 0-iSin. matrix. 

The miniature switch SI could very well be part 
of the potentiometer VR1 which would save some 
space. If this is done make sure that the pot. is wired 
so that clockwise rotation of the pot. decreases its 
resistance. 

The checker will be found very useful indeed in 
matching small values of capacitance where precise 
values are not important. In practice changes of less 
than IpF can be detected. 

Don't forget that the Small-C Checker can still be 
used as a frequency spotter with its internal 1MHz 
oscillator. Connect a short stiff wire to the live 
terminal and harmonics can be found up to at least 
30MHz. ■ 



1066 



BI-PAK SEMICONDUCTORS 



SILICOK RECTIFIERS— TESTED 

PIV 300raA 750mA 1A 1.5 A 3 A 10 A 30 A 

50 4p Sp 5p 7p 14p Sip 47p 

100 4p Sp 5p 13p 18b 23 p 75b 

200 Sp 9p flp 14b 20b 34p £1 

400 8p 13p 7p 20b 27 p 37p£125 

600 7p lBp lOp 23b 34b 45p£18a 

SOO 10b 17p 13p 25 p 37 p 55p £2 

1000 lip 25b 15p 30p 48b S3p£2 50 

1200 — 83p — 33b 57p 75p — 



NEW LOW PRICED TESTED S.C.B'l 



100 
200 
400 

eoo 

SOO 



1A 
TOS 
23p 
25p 
35p 
43p 
53p 
83p 



T066 T066 
ESp 47p 



7A 10A 



47P 
B7p 
70p 



S8p 
57p Blp 
67p 7Sp 
77p 87p S1-2S 
SOp £120 £1 50 



16 A 30 A 

T048 T048 

63p £115 

63p £140 

75p £1-80 

flap £175 



£4 



2A POTTED BRIDGE RECTIFIERS. 200 V. 5 Op 



TRANSISTOR EQUIVALENTS BOOK. A com- 
plete cross reference and equivalent book for 
European, American and Japanese Transistors. 
Exclusive to BI-PAK. 75p each. 



DUAL-IN -LISE LOW PROFILE SOCKETS 

14 AST* IB Lead Sockets for use -with Dual- in - 

Line Integrated Circuits 



Order No. 

TS0I4 14 pin type 

TS016 16 pin type 



Flics each 

] -24 25-99 100 up 
33p 27b 25p 
43p 37p 34p 



2N2060 NPN SIL. 
DUAL TRANS. CODE 
D1699 TEXAS. 
OUR PRICE 25p each 



S||, trans. suiinVjlc 
Jor P.E. Organ. Metal 
TO-18 Eqvt. ZTX30O. 
5p each. Any Qty. 



EX-EQUIPMENT 

■nun 

AF117 transistors. Large can 4 lead type. 
Leads cut short hut still usable, real value at 
15 for 50p. 



TBUGS. 

2 A 8 A IDA 
VBOM TOS 1066 T048 
100 SOp 63b £1 

200 70p 8 Op £125 

400 90p £1 £1 80 

VBOM— Blocking volt- 
age In either direction. 



SILICON DIAC 

For use with Triacs 

BR100 87p each 



BRAND NEW TEXAS 
&ERM. TRANSISTORS 
Coded aad Guaranteed 
Pak So. EQVT. 

Tl 8 20371A OC7I 
T2 8 2G374 OC73 
T3 8 203744AOC81D 
T4 8 203SIA OC81 
TB 8 20382T OC82 
Tfi 8 2G344A OC44 
T7 8 2 0345 A OC45 
T8 8 20378 OC78 
T9 8 2 (4399 A 381809 
T10 8 20417 AFH7 
All 50 p each pack. 



CADMIUM CELLS 

OK PI 2 43p 

ORP60, QRPfll 40p each 



PHOTO TRASS. 
OCP71 Type 43b 



FREE 
One SOp Pack o! your 
own choice tree with 
order* talned £4 or over. 



SIL. G.P. DIODES 
300m W 30 50p 

40PIV iMIn.) 100 £1-60 
Sub-Mln. 500 £5 

Full Tested 1 000 £9 
Ideal for Organ Builders 



OlIDCD DA KG NEW BI-PAK UNTESTED 

oUrCR rnlVa semiconductors 

Unequalled Value and Quality • 

Satisfaction OUARANTEED In Every Pak, or money back. 

Pak Ho. 

ITt 120 GLmi auh-mln. Beneral Purpose fteniianiiiin DlodeB 50p 

U2 60 Miied Germanium Tranaistors AF/RF 50p 

U3 75 German mm Gold Bonde d Ptodm aim. OA5. OA47 ., SOp 

Vi 40 Germanium Transistorg like OCfll, AC12H SOp 

US 60 2O0mA Bub-mln. Bil. Dlodea BOp 

US 30 Silicon Planar Translators NPN elm. USY95A, 2X706 SOp 

U7 18 Silicon R ectifiers Top-Hat 750uiA up to 1,000V SOp 

L'8 50 SH. Planar Diodes 250mA OA/200,'202 SOp 

U9 20 Miied Volte 1 watt Zener l)iode» SOp 

Ull 30 PMP Silicon Planar Transistors TO-5 aim. Bit 1132 ■■ SOp 

U18'" 30 PNP-NFN Bil. Transistors OC200 ft 2S104 ,..,... SO p 

17 14 100 MUeil Silicon and Germanium Diodes SOp 

1*18 25 KPN Silicon Planar Transistors TO-5 nini, 2N697 SOp 

Uia 10 3-amp Silicon Rectifier* Stud Type up t o 1,000 PIV . . BOp 

U17 30 Germanium F5P AF Trftin ist-ii ts TO-'r. lik e ACY 17-2 2 SOp 

U18 8 0-Amp S ili cOD Rectifiers BYZJ3 T ype up lo 6O0 PIV SOp 

UI9 25 Silicon NPX TrannlHtop- lik* HCI0H SOp 

U 20 12 1-5 amp Silicon Rectlflere Top-Hat up to 1,000 PIV . ■ SOp 

U2I 30 AF Germanium alloy Transistors 2C1300 Ser. & OCT I . . S Op 

U23 30 Madt's like MAT Series FNP Transistors 50p 

U24 2 Oarmanturo 1-amp Rectifiers GJM up to 300 PIV BOp 

b'25 20 BOOMo/e WPS Silicon Trarntotoni 3N70H. HSY27 '".'.' 50p 

1128 SO Fast B witching Silicon Diodes like lN'JU Micro-min. - Mp 

U28 Experimenters' Assortment of Integrated Circuits, un- 

test ed, tlaten. Flip - '■• lops. Registers, etc. 8 Assorted Pieces £1 

U29 10 1-amp SCR'e TQ85 can up to 600 PIV C RSI/25-600 .. £1 

U31 20 811. Planar HP'S trans, low noinc Amp 2K3707 .... SOp 

U32 25 Zener diodes 400mW D07 case mined VJg Sj 3-l!i ...... SO p 

U33 10 Plastic case 1 amp Silicon Rectifiers 1 ^400fi siTics . . _50B 

U34 30 811. PNP alloy tranji. TO-5 BCT2-1. J s:< H2/4 S Op 

U 35 25 Bil. Planar trans. PXP TO-18 ■2N'2flQ fj 50p 

V Si 2S 811. Planar SPS trans, TO-5 BFY5t)fSIB2 SOp 

t'87 30 8U. alloy tram. SO-2 PN'F, OC2Q 23328 fljj 

U3S 20 Faiit Switching Bil. tran s. NTS 400 <le'i 2N'.1iil l SOp 

U3 9 30 RF Qerm. PXP tranj.. 2NI303/5 TO-0 , SOp 

U40 10 Dual trana. 8 lead TO -5 2X2060 SOp 

041 20 RF Germ. Irans. TO-1 0045 NKT72 "'. . .". S Op 

U4l i6~VHF Germ. PXP trans. TO-1 XKT687 AF1I7 SOp 

Code No*, mentioned above are given as a (rulde to the type of device 
in the Pak, The devices themselves are normally unmarked. 



UNIJUNCTION 
UT48. Eavt. 2S2646 Eqvt. 
T1S43. BEN3000 27p each 
25-99 25p, 100 UP 20p 



NPN SILICON PLANAR 
BG107/S/9 lOp each, 50-99 
Bp. 100 up gp each, 1,000 
off, 7p each. Folly tested 
and coded TO-18 case. 



1S0VCB NIXIE DRIVER 

TRANSISTOR 

Sim. BSX21 and C407. 

2K1893 FULLY TESTED 

AND CODED SD120, 

1-24 17p each. TO-5 NPN 

25 up 15p each. 



AD181 -VPjV 

AD 188 FlfP 

OUR LOWEST PRICE 

OF B3p PER PAIR. 



SU3055 1.15 WATT SIL. 

POWER. NPN. 
OVR PRICE 63p Ed.CH 



FET'S 
2N3819 
2N3820 
11PF105 



40; 

£1 
43p 



PRINTED CIRCUITS 
EX-COMPUTER 
Packed with semiconduc- 
tors and components. 10 
boards give a guaranteed 
30 trans, and SO diodes. 
Out price 10 boards 50p-r 
10p p. 4 p. 
100 boards £3— 30p p. & p. 



FULL RANGE OF ZENER 
DIODES 

VOLTAGE RANGE 8-SSV. 
400mV (DO-7 Case) 13p ea. 
1-5W (Top-Hat) 17p ea. 
10W (SO- 10 Stud) 25b ea. 
AH follv tested 5% toL and 
marked. State voltage 
required- 




Price and «ty. Pricei 
1-24 20-90 100 up 

23p 20p 15p 



BI-PAK -LOW COST I.C's 



BI-FAK Semiconductors now offer you the largest and most 
popular range of I.C's available at theye EXCLUSIVE LOW 
PRICES. TTL Digital 74N Series fully coded, brand new. Dual 
in-line plastic 14 and 16 pin packages. 



DescrtBtion 

Quad 2-Inpnt NASD GATE 

Quad 2-Input NASD GATE— OF t.S COL- 
LECTOR 

BlEX ISVERTER 

Triple 3-Input SAND GATE 

Dual 4-Input SAND GATE 

Single 8-lnput NASD GATE .. 

Dual 4-lnput BUFFER GATE 

BCD to decimal decoder and N.I.T. Driver . . 

BCD to decimal decode (TTL O/Pl 

Dual 2-Input AND/ OR/NOT GATE— expand- 
able . . ■ ■ ■ • ■■ ... «■ ■ ■ 

Single 8-lnput AND/OR/NOT GATE— expand- 
able . . . . ■ ■ 

Dual 4-Input — expandable ■ 

Single IK Flip -Flop— edge (ricgercd 

Single Master Slave J K Fliti-Flop 

Dual Waster Stave JK Flip-Flop 

Dual D Flip- Flop 

Quad Bistable Latch 

Dual Master Slave Flip-Flop with preset and 
clear 

Four Bit Binary Adder 

BCD Decade Counter 

Divide by 12 4 Bit binary counter 

Divide by 10 4 Bit binary counter .. 

Dual Entrv 4 Bit Shift Register 

4 Bit Up-Down Suift Register 

5 Bit Shift Register 



BP04 7404N 
BP10 7410N 
BP20 7420N 
BP30 7430N 
BP40 7440S 
BP41 7441 N 
BP42 7442S 
BP50 7450S 

BF53 7453N 

BP60 7460N 
BP70 7470N 
BP72 7472N 
BP73 7473N 
BP74 7474S 
BP75 7475S 
BP76 7476N 

BF83 7483N 
BF90 7490 N 
BP93 7492N 
BP93 74935 
BP94 7494N 
BP95 7495S 
BP96 7496N 

Data is available for the abov 



23p 
23p 

sap 

23p 
£3p 
23p 
£1-21 
87p 



20p 
SOp 
SOP 
20p 
20p 
20p 
£1-00 
77p 



23p SOp ISp 



23p 
S3p 
3Sp 
35b 
43p 
43P 
55b 



SOp 

20p 
32p 

32p 
40p 
4 Op 
SOp 



47p 45p 

£1-10 il-00 

87p 77p 



87p 
S7P 
87P 
87b 
£1-10 



T7p 
77p 
77p 
77p 
£1-00 



15p 
15p 

!.«ln 

29n 
37!. 
37B 
47p 

13p 
SOp 
87p 
B7P 
67p 
67P 
B7p 
BOp 



TTL INTEGRATED CIRCUITS 

Manufacturers* "Fall outs"— out of spec, devices including functional units and part 
functional but classed aa out of spec, from the manufacturers very rigid specifications, 
ideal for learning about I.C's and experimental work. 

PAK IP. 

r Id hi 12 
UIC01 - 12 
UIC02 - 12 
UIC03 - 12 
UIC04 = 12 
UIC03 =12 
UIC10 - 12 
UIC20 = 12 
U1C40 = 12 
UIC41 = S 
LIC42 - S 
UIC50 -=13 
UICSl = 12 

no;" - 12 

UIC70 ~ B 

UIC73 = 8 

Packs cannot be split but 20 assorted pieces (our mix) is available as PAK LICX1. 

Every PAK carries our BI-PAK Satisfaction or money back GUARANTEE. 







PAK No. 








7400N 


SOp 


LTC73 = S 


X 


7473S 


SOp 


7401 N 


SOp 


UIC74 = 8 


X 


7474N 


50p 


7402N 


SOp 


UIC75 = 8 


X 


7475N 




74035 


50p 


UIC76 = 8 


X 


747-5 S 


SOp 


74045 


SOp 


UICSO = 5 


;•: 


74B0N 


5up 


7405N 


SOp 


UIC82 = 


X 


74ViN 




7410S 


SOp 


UTCS3 = 3 


X 


748 35 


SOp 


742 ON 


SOp 


UICS6 = S 


X 


7486N 


SOp 


7440N 


SOp 


ricoo = 5 


X 


7490N 




7 44 IAS 


BOp 


UIC92 = 5 


X 


7492S 


SOP 


7442S 


SOp 


UIC93 = 6 


X 


74935 


SOp 


74505 


SOp 


UICS4 = S 


X 


74945 


SOp 


745 IS 


SOp 


UIC95 = 5 


X 


7495N 


SOp 


7460N 


SOp 


ncas - 5 


X 


7496N 


SOp 


7470N 


SOp 


UICX1 =2S 


X 


ASST'D 


74's £1-50 


7472 N 


SOp 











Type 



POWER TRANS. 
Price 
each 



OC20 

OC22 

OC23 

OC25 

OC26 

OC28 

OC29 

OC35 33p 

OC3B «p 

AD140 40p 

AD142 40p 

AD149 48p 



50p 
30p 
33jj 
25p 
25p 
40p 



Seriep of I.C's In booklet fo rm price 12 'p i':u:h 
1 



D13D1 Silicon Unilatera 

twitch BOp each. 
A Silicon Planar, mono- 
lithic integrated circuit 
having thyristor electrical 
characteristics, but with an 
anode prate and a built-in 
+ '2ener" diode between 
gate and cathode. Full 
data and application cir- 
cuits available on request. 



Sutplni A.E.I. 40A Germ. 
Junction Rectifiers. For 
Power Applications. 
Type GP6C20 400PIV 40p 
CPBC30 60OPIV SOp 



AFQ39 PNP 8BBH. 
SIEMENS VHP TRAN- 
SISTORS. RF MIXER 4 
OHC. UP TO P00 MHZ. 

USE AS REPLACEMENT 
FOR AF13P-AF186 & 100's 
OF OTHER USES IS 
VHF. OUR SPECIAL 
LOW PRICE : 1-24 87p 
eath, 2A-99 34p each 
100+ SOp each. 



SILICON HIGH VOLTAGE 

RECTIFIERS 
1 0-Amp 3-K.V. (3000 
P.I.V.) Stud Type witb 
Flying Lead*. BOp each. 



RTL FAIRCHILD (U.S.A.) I.C's 

RTL Micrologic Citcuili . , 8^; <"*'*» ™ e *- 

Kpoxy case To- 5 temp, range 15°U to E5°C . . . . 1-11 1---4 

iiL 900 Bnfler - ■ ■ • 40b 35b 

uL 914 Dual two-Input GATE 40p 35p 

tih 023 J-K Flip-Bop 53p SOp 

Full data and clrcuit» for IC'« In Booklet form price 7p each. 



2.T-M9 

33p 
33p 
47p 



100 + 
27 P 
27p 
45p 



Type No. 

BP201C— SL20/C 
BP701C— SL70/C 
BP702C— 8L702C 
BP702— 72702 
BP709— 72709 
BP709P— (1A709C 
BP741— 72741 
(*A703C— JAA703C 
TAA2H3 
TAA293 



LINEAR I.C's 

Caie Leadi Description 



TO-5 

TO-5 

TO-5 

D.I.L. 

D.I.L. 

TO-S 

D. T,L. 

TO-5 

TO -72 

TO-74 



Price 

1-24 23-89 

G.P. Amp 63p 53p 

OP Amp 03p BOp 

OP Amp Direct O/P. . 83p SOp 

G.P. OP. Amp (Wide Band) S3p *5p 
High OP Amp . . 53p 45p 

High (lain OF Amp . . 53b 45b 

High Gain OP. Amp (Protected) 76p 80b 
R.F. — IF Amp . ■ 43p 35p 

A.F. Amp 70p SOp 

G.P. Amp BOp 75p 



ALL PRICES IN NEW PENXIE. 
Please tend all orders direct to our warehouse and despatch department. 

BI-PAK SEMICONDUCTORS 

P.O. BOX 6, WARE, HERTS. 

Postage and packing add 7p, Overseas add eitra lor Airmail. Minimum order SOp. 
Cash with order please. GIRO 5o. .i«3-/Wt> 



1067 



TECHNICAL 
TRAINING 

in radio television 
and electronics 



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POST THIS COUPON TODAY 

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Selections from FELSTEAD ELECTRONICS' List 

(Sent free lor stamped Addressed envelope to address below) 

Tn.n«iitor« etc. AC123 lEjp. AF116 ISp. A116 15p. AF117 BOn. OAo 7ip. OA10 Tip. 
QA81 7ip. OAS6 7|p. OC23 821p. OC25 8up. OC26 37|p. OC28 421b, OCS5 4Blp. 
OC44 Up. OC46 12jp, OC71 12lp. OC72 12jp. OC75 18iP. OCS1 12frp. OC81D 121p. 
OC82D lBfcp. OC170 BOp. OC171 12Jn. Many more in list. 8.D.B. BY100 800piy 14p. 
S amp lerlet: BVZ13 3O0ph- 20p. BYZ12 600piv B6p. BTZ11 900piv, 80p. BYZ10 
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speed Bi', all parts replaceable, highest quality, full guarantee; H.-71 (10p.). DIAMOND 
BTSTLU Replacements for HSR TC8/LP, TC5/8. TC8LP/STEKBO : COLLAEO 'O': ROJT- 
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MONO Gr (17/2 75p. HTttREOCOMPATLBLE (MONO) 0P31/aC (11.05). STEREO GP9S 
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GOLD RING 0850 £4-B7 t . G800 £8-60. O80OE £13.50, G800 SUPER E £19-50 (6}p all types 
or Be*. Port. E2JP,). STYLTI FOR ALL ABOVE TYPES, Including GOLDRING available. 
RECORDING TAPE. St ill the finest quality British Mylar available: Standard 5*600 ft. 38p. 
51" 0*0 ft. S&J.7" 1200 ft. S8p. LONG PLAY 5* 900 ft. SOp. 5f 1200 ft. 66p. 7* 1800 ft BOp 
{7»p on 0- and 6 J', &P on 7'). MICROPHONES Crystal Mic 91, hand/desk 81p. MIC45 
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15p), Type 209 Cardioid ball, 5OK/60O £1, omni-dir„ built-in vol. control, on/off switch, 
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cable, adaptor S8'87fr (27Jp either). BHCROPH0KE INSEETS. Dia., 1-75* OR 0-9- either 
size 27fp (8p), EARPIECES with lead * mln. jack plag (2-5 or 3-6 mm., state which) 
MaRiietic 9p Crystal (3-5 only) 24p (Up to 3 for 6p on any). HEADPHONES De-iuie 
STEREO 8-16 Ohms, £2-47$. 3ame, fitted vol. control each earpiece £4-20. Both have 
lew! and stereo Jack plug (17*p). HIGH RES. 2000 ohm, Adjustable 92tP (12ip). SPEAK- 
ERS. 12* ROUND fitted tweeter. 3 or 15 (1 (state which! £1-871 (271) or lor Stereo £4-25 
padr.carr. paid. 2,* 3 OR 8Q (state which) 3?£p (6p). EMI13*i 8-^ 3, 8 or 15 ii (State which) 
£21EJ (25p): with single flared para, tweeter cone 8 or 15 Q (state which) £2 27f (25p): 
with two tweeters and crossover network 8 or 16 (state which) £3-75 (25p). VIBRATORS. 
Genuine Pleesey 12V 4-pin non-synch. I21HD4, 2}* ex. pine. 27ip. Am. 12V 4-pin non- 
synch. 7/l«ths. longer. S2H». ViV 7-pin Synch. (12SR7) 62ip (ATI types Otp per vibrator). 
CONNECTING WIRE. Packs of 5 coils asstii. cols. ea. coil 5vris. Solid" core 14p (6p). Flexible 
18P (71p). Super thin tor transistor wiring 18p (8p). PICK-UP WIRE. Super thin twin flex, 
screened and sheathed 8p yd. [Sp ap to 6yds. — over free). RETRACTABLE Flex. Leads. 
(Ourliea) 6(t. phonoplng ea. end 22}p. 1 2 (t. 38p . 6ft. phono plug/phono MH*et other end 
86p. 12ft. 42lp. (6p per lead all types). BATTERY ELIMINATOR. 240V AC input 3, 6, 7* & 
9 V DC output at 400 m'a. Two switches' leads' pilot light and universal adaptor for all trans, 
appliances Including all makesc assette tape record ere and players £3-15 (24p). SEND 8AE 
tor full free lists — Teleton anc small 3W and 7JW trans, amplifiers. Electrolyties, Vol. 
Controls, all typea of radio swltehes, car and portable expanding aerials. Meters, Test prods, 
all typeaof Brit. & cent, standard and min. pings and sockets, SDE's Thyristors, croc, clips 
(various) terminals, etc. etc. and many "Special Offer" lines at lowest possible prices. 

FELSTEAD ELECTRONICS (PW43) 

LONGLEY LANE. GATLEY, CHEADLE, CHES. SK8 4EE 

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SEND S.A.E. OR CALL AT ANY BRANCH FOR YOURS 1 




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6'ln. 900ft. 10/8 5fin. 1,800ft. 19/8 
7in. 1,200ft. 18/B 7in. 3,400ft. 87/- 

Long Play Tripla Play 
Sin. 225it. 2/fl 4 in. 900ft. 13/- 
4in. 450ft. 5/6 5in. 1,800ft, 25/- 
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on 

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obtainable from your local Retailer 
Trade enquiries to : 

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Technical enquiries lo : 
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Industrial Estate, Chandler's Ford, Hants 




1068 



GOING BACK 




EVERY day of the week, except when there is 
a postal strike, we receive letters from readers 
interested in the Going Back article. The 
Reverand R, J. Mantle, M.A., from Aberdeen writes 
that he has a B.T.H. crystal wireless dated 1924 and 
another B.T.H. valve/crystal set with two crystals 
and one valve dated about 1927, He says that 
amongst his books on wireless, his most precious is 
a book entitled "A Beginner in Wireless" by E. 
Alexander, published in 1923. It has many interesting 
photographs like Marconi's Timed Spark c.w. Genera- 
tor, the Brown Microphone Amplifier and Fleming's 
thermionic valves. 

One suggestion that Reverand Mantle makes is 
that wireless of the 1920's should be known as 
"Veteran Radio" and that of the 1930's should be 
known as "Vintage Radio". — Any comments? 

C. Langton Kirk writes to say that he has seen 
the name of N. Gilbertson mentioned in our August 
1970 issue and wonders if this is the same one that 
he knew as a very good friend back in 1925-26. Both 
were interested in wireless as a hobby in those days. 
So, Mr. Gilbertson, if you worked in a cinema in 
Leicestershire in 1925, you are the correct man and 
Mr. C. Langton Kirk, 137 Hubert Road, Bournbrook, 
Birmingham, 29 6ET would like to hear from you. 

Mr. W. G, Rumbold, M.I.E.E., tells us how he used 
to listen to the "shipping bands" on 600m where 
there was a constant stream of traflk in readable 
Morse always on tap. A little higher up in wave- 



Mr, Cummlngs' 
receiver and 
speaker (f925). 



ARTHUR DOW 

length, (frequency was not spoken of then) were Croy- 
don Airport, Castle Bromwich and Le Bourget with 
R/T on 900m. 

Mr. F. C. Burgess, 58 Beaconhurst Drive, Beacon 
Bay, East London, C.P., South Africa, writes to say 
that he has in his possession an old Marconiphone 
two-valve set. He estimates its year of manufacture 
at approximately 1923, The set is still in good condi- 
tion with its two plug-in coils and a small name-plate 
is affixed bearing the inscription "Marconiphone V2. 





Marconi Morse practice buzzer, 



Type R.B.I.A., A.S.206B Inst. No. C-A-7618." If any 
readers have any idea of the exact date of manu- 
facture, will they drop a line to Mr. Burgess please? 

A photograph we received the other week is of 
a Marconi Morse Practice Buzzer. Vintage is 1912. 
Slightly different from a modern transistor Morse 
oscillator, this one boasts a highly finished teak board 
on which is mounted an operating key and other 
parts. Enclosed in a case on the same board is a 
battery, high note buzzer and induction coils, one of 
which is provided with a convenient handle, by 
means of which the strength of signals in the tele- 
phone can be varied. The buzzer is arranged in a 
practically sound-proofed box, but can be removed 
for easy adjustment. A single head piece telephone 
was provided with the instrument, but a double head 
piece could be supplied if required at slightly 
increased cost. 

Keith Cummins — better known to our sister maga- 
zine "Television" readers for his 625-line TV Receiver 
articles, sends us a photograph (left) of a receiver 
he has recently put in working order. It employs 
two valves and a 4-5V battery has been used for 
the l.t. supply giving each valve 2 -25V in a series 
circuit. Keith says this helps since they are so ancient 
—and he is highly delighted by the performance. 
Date is approximately 1925. 

1069 



Wiultii experiment* on an Aeroplane 




Flanders' monoplane on which experiments with wireless were carried out in 1912. 



One of our vintage radio enthusiasts, Mr. Leonard 
Adlard of Essex recently loaned us some copies of an 
old magazine called The Marconigraph — the official 
organ of the Marconi Co. AH dated 1912, these maga- 
zines have some real gems of information in them 
and below we publish an extract which tells the story 
of an early exploit with an airborne transmitter. 

"One of the applications of wireless is telegraphing 
from aeroplanes, airships and balloons. The advan- 
tage of being able to communicate with land or other 
stations whilst in the air has been well exemplified 
on many occasions. 

On March 16th, 1912 when some wireless experi- 
ments were being carried out on Mr. Howard 
Flanders' monoplane at Brooklands Aviation Grounds 
near Weybridge, a curious incident occured. On the 
previous evening a trial flight was made after the 
wireless apparatus had been fitted to the machine 
and everything seemed in perfect working order. On 
the Saturday morning, as the weather was exceed- 
ingly favourable for flying, the machine was taken 
out again, but it was then that the mishap occured. 
The aviator was flying very low at the time, and on 



landing his first skid apparently struck the ground 
owing to a too sudden descent and to the speed at 
which the aeroplane was moving at the time — approxi- 
mately 60 miles per hour — the machine turning com- 
pletely over. The aviator was thrown out of his seat, 
and when picked up was unconscious. The fuselage 
of the machine was smashed to two places and the 
propellor was also damaged. The wings had ap- 
parently escaped unhurt, but had to be stripped of 
their fabric and thoroughly overhauled. The exhaust 
pipes, radiators, and lubricating pipes on the engine 
were also damaged and the front skid of the aero- 
plane was broken in two. Amidst the debris, it would 
not have been surprising if the wireless apparatus 
had been smashed, especially as the oil tank beside 
which the wireless apparatus was fitted had been 
severely battered and was leaking badly. After re- 
moving the sand and dirt with which everything was 
covered, it was found, however, that the wireless 
apparatus had escaped quite undamaged and was in 
working order; even the aerial wire, which was 
attached to the broken fuselage remained intact!" 
— Amazing! 



c<&! €<&i cat c<©! cai 

if you have a Vintage CQ you would like included In Practical Wireless, 
drop a line to Colin Riches and Arthur Dow who will Include It In 
the earliest available Issue. 

APPARATUS REQUIRED 

. , . ex-Cable and Wireless Morse Operator (now alas tele- 
type) wishes to acquire two early Morse keys (brass) to 
cherish and use on the amateur bands. — J. A. Van Walwyk, 
G3YRW, 321 Parkside Avenue, Barnehurst, Kent. 

... I am interested in knowing if anyone has any Telsen 
baseboard components which were produced in 1933. They 
include the dual-range coU, the combined dual-range short 
wave coil unit, the h.f. coil, screened tuning coils (pair or 
singles) and the twin tuning condenser with the built-in 
trimmer to match the coils. Also the 4, 5 and 7 pin valve 
holders. — G. Beasley, 31 York Avenue, Bedworth, Nr 
Nuneaton, Warks. 

1070 




For those readers who have asked to see a close-up of the Walters 
Receiver (News . . . Jan. 1971), 




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RESISTORS 

Code Pawn Tolerance 

C 1/20W B% 82Q-220KO 

C 1/8 W B% 4-7ft-330Kfi 

C 1|4W 10% 4-7Q-10Mfi 

C 1/2W o% 4-7D-10MC1 

C 1W 10% 4-7Q-10MQ 

HO 1/2 W 2% 10 0-lMfl 

WW 1W 10% ± 1/20 £5 0-22Q-S-9C1 

WW 3W B% 1211-lOKn 

WW 7W B% 1211-lOKa 

Codei : C = carbon film nigh stability low noise 

MO = metal oxide Electrosil TR5 ultra loir noise 
"WW = wire wound Flessey. 
Value*: 
E12 denotes series: 10, 12. IB, 18, 23, 27, 33, 39, 47, 88, 

88, 82 and their decades. 
E24 denotes series: as £12 pins 11, 13, 16, 20, 24, 30, 36, 

43, 51, 62, 76, 91 and their decades. 



lie! 



l-S 

2 -a 



10 to 99 
(tee note below) 
6-6 
N 
O'S 
1 
2 

M 



100 op 



0-7 
0-9 
l-S 



Velna* 

ITailsble 

El 2 

£24 

El 2 

E24 

E12 

E24 

E12 7 7 I 

B13 7 7 6 

E12 9 9 S 
Prtett art In rtrvx each fur i<rm< oSmtc value and potctr 
rating, NOT mixed taltut. {Ignore Irattltnu of \p. on total 
value, of retittor order) 



INTEGRATED CIRCUIT 
AMPLIFIERS 

SINCLAIR IC10 complete with instruction book giving 
amplifier circuit details and range of applications, 

IS-BS nett. 
Components pack lor stereo inc. mains transformer, 
controls etc. 14-75 nett. 

PLESSEY SL403A Now only x210 nett SW into 7-aCl lor 
18V supply. Application data sent with two more. 



WAVECH ANGE SWITCHES 
LONG SPINDLES 

IP 12W; 2P 8W; 3P 4W; 4P 3W 
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NEON INDICATOR LAMPS 

all 200/2SOV. Square bezel, red only ISp 

Bound chrome bezel red, amber, clear 24 p each 

Toffle iwitebei, 2S0V a.c. i-ba. 

chrom e dolly and chrome milled nut S.P. $ .T. Up, 3. P . D . T . 
SSp D.P.D.T. SSp; S.PJ>.T. centre off SOp 



B-DeC'i put an end to "birdsnestiiig". Components Jnst 
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MULLARD polyester C280 series 

2B0V 20% 001; 0-233; 0-033, 0-047 Sp ea. 068; 
01, 018 4p. 0-22 Sp, 10%: 0-33 7p, 0-47 8p, 0-68 lip, 
l*iF Up. i"5uF Blp, 3-S^F 2*p. 

MULLARD SUB-MI N ELECTROLYTIC 

C42S range siial lead Sp each 

Valnss (uF/V): 064/84; IMS; 1-6/2S) 2-6/18; 2-5/64; 4/10; 
4/40; 5/64; 8-4/6-4; 6-4/2B; 8/4: B/40; 10/2-B; 10/18; 10/64 
13 -6/35; 16/40; 30/16; 20/64: 28/6-4; 2B/2S; 32/4; 32/10 
32/40; 82/64; 40/16; 40/3-6; 60/6-4; 80/25; 60/40; 64/4 
64/10; 80/2-fl; 80/16: 80/25; 100/8-4; 128/4; 138/10 
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High ripple current types: 1000/25 SSp; 1000/50 4Ip 
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6000/100 12-91; 10000/15 SSp; 10000/25 11 BS; 10000/ SO 
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Axial leads: 60/50 Sp: 100/25 Sp: 100/50 ISp; 250/28 Up: 
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Axial leads: 4-7/10: 4-7/28; 6/60 Sp ea. 10/10; 10/25; 
10/50; 33/10; 50/10 Sp e*. 32/38; 25/50; 47/25; 100/10; 
220/10 Spea. 



COPPEB WTEE even No 8.W.O. only. 
3oi reels 16,22 8.W.O. SSp: 24-SO 9.W.O. SOp; 32-34 B.W.G. 
SSp; 20-40 S.W.O. SSp; 4oi reels 16-22 S.W.G. only 4Sp. 



PEAK SOUND PR0DUQS 
ENGLEFIELD 12+ 12 WATT AMPLIFIER 




Bt«reo ampHQer in moduUr kit lorm 1'2 watts per channel 
£38 '45; Cabinet kit only £8. These priced nett. 
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BAXANDALL SPEAKER SYSTEM 

Designed by Peter Bax&nuall, 
Snperb reproduction for its 
size. Handles 10 watts with 
ease. Uses ELAC 15 Q S9BM109 
speaker Unit Kit £13-90 nett; 
bnilt S19-40 nett. 



Bi 



MAINLINE AMPLIFIER KITS 

RCA ; ar,9 designed main amplifier kits. 

Input eensiHvtty 5OO-700mV for full output into 8 £1. 



12W 
2SW 
40W 
70W 



Kit price 


Suitable unreg 


including 


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components 


kit 


£S-40nett 


£4-60 


£9-50 nett 


K/A 


£10-50 nett 


£575 


£12-60 nett 


£094 



30 WATT BAILEY AMP. PARTS 

Sensitivity 1.2V for fall atrtpot Into SO 

Transistors and PCB for one channel £0-40 

Transistors and PCB for two channels 112-80 

Capacitors and resistors (metal oxide) £2 00 per channel 

Complete unregulated power supply kit £4-75 



ZENER DIODES 

5% lull range E34 -rulues; 400mW; 2-7V to 30V 15p each 
1W: 6-8V to 82V SSp each 1-5W: 4-7V to 7BV SOp each 
Clip to increase 1-SW rating to 3 watts (type 266F) 4p. 



CARBON TRACK 
POTENTIOMETERS, long spindles 

Double wiper ensures minimum noise level. 

Single gang linear 220 Q, to 2-3Jin 12p 

Single gand log 4-7K Q to 2-2M fj ISp 

Dual gang linear 4-7K O to 2-2M Q 42p 

Dual gang log 4-7K ft to 3-3M Q tSp 

Log/antilog 10K. 47K, 1MO only 48p 

Any type with |A D.P. mains switch, extra ISp 



Pltaie note: oniv decades of 10, 
within rangee quoted* 



22 and 47 are auai table 



CARBON SKELETON PRESETS 

Small high quality, type FH, linear only 100 Q, 220 £1 
470 (1, IK, 2K2, 4K7, 10K, 22K, 47K, 100K, 220K, 470K, 
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each. 



THIS MONTH'S HIGHLIGHT OFFER 

High grade audio transistor TYPE 3K3055— Mai. 
dissipation 115 watts at 25°C. Max. volts 100 Vcbo, 
The lowest priced of its kind. Ideal for up to 20KHi and 
heavy duty switching. 7Sp complete with insulating set, 
ea. suggested complementary drivers BFX29/BFK84 
per matched pair S4p. 



COMPONENT DISCOUNTS 

10% on orders (or iMMBponenta for £5 or more. 15% an 
orders for rampouenta for £15 or more (No discount on 
nett items), 

POSTAGE AND PACKING 

Free on orders over £2. Please add lOp if under. Overseas 
orders welcome: carriage charged at cast. 

PAYMENT BY CHEQUE 

To avoid delay and comply with the law cheques must 
he drawn In decimal currency in U>K H 



ELEGTROVALUE 



(Dept. PW.371) 28 ST. JUDES ROAD, ENGLEFIELD GREEN, EGHAM, SURREY 

Hours: 9—5.30: Sat. 1 p.m. Tel.: Eg ham 5533 (STD 0784-3) Telex 264475 



1071 




TV 



RADIO & TV CQMPONENTSlActoniLtd 

Post Co 

21c HIGH STREET, ACTON, LONDON W.3. 6NG 
Personal shoppers to 323 Edgware Road, London, W.2. 
ALL ORDERS BY POST TO OUR ACTON BRANCH 

Terms C.W.O. All enquiries S.A.E. 



Stereo 



■ 









VSMTH 

viscoutr 

F.ET 

TKBT 



This superb stereo system is a real prjce break through. It comprises the 
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Measuring 17±in x 10|in x 62in, the Duo typ|e 2 speakers are teak finished with 
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Complete stereo system £43 plus £2*50 p. & p. or with Mk tl 
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^T°tir * f - e - t - Mk| - 114 * 25 + s °p- p- & ?• 



High fidelity transistor stereo amplifier employing field effect transistor*. With this 
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Specification— Output per channel 10 watts 
r.m.s. Into 3 ohms Frequency bandwidth 
20 Hz to 20 kHz + 1db at 1 watt. Total 
distortion at 1 kHz at 9 watts 0.5% Input 
sensitivities CER. P.U. 100mV Into 3 meg 
ohms. Tuner 100mV Into 100K ohms. Tape 
lOOmV into 100K ohms. Overload Factor 
Better than 26db. 



The £25 
Stereo system 



The Duetto is a good quality stereo 
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previously associated with amplifiers 
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SPECIFICATION— 

R.M.S. power output 3 watts per 
channel into 10 ohms speakers. 

INPUT SENSITIVITY. Suitable for 
medium or high output crystal cart- 
ridges and tuners. Cross-talk better 
than 30dB at IKc/s. 

CONTROLS: 4-position selector 
switch (2 pos. mono and 2 pos stereo) 
dual ganged volume control. 

1072 



Signal to noise ratio— 70db on all inputs 
(with vol. max). Controls— 6 position selec- 
tor switch (3 pos. stereo and 3 pos. mono). 
Separate volume controls for left and right 
channels. Bass ± 14db at 60 Hz. Treble 
(with D.P.S. on off) ± 12 db at 10 KHz. 
Tape recording output sockets on each 
channel. Size 12±in, 6in. 2fin. in simulated 
teak case. BUILT & TESTED. 



Mkll (MAG P.U.) £15.75 plus 50p. p. & p. 
Specification same as Mk. 1, but with the 
following inputs. Mag. P.U. CER. P.U. 
Tuner. Spec, on Mag. P.U. 3mV at 1 kHz 
input impedance 47K. Fully equalised to 
within ±1db RIAA. Signal to noise ratio— 
65db (vol. max). 




TONE CONTROL Treble lift and cut 
Separate on off switch. A preset 
balance control. 



Duetto integrated transistor stereo Amp. 


£9.50 37p 


Garrard Changer from 


£7.97 37p 


Cover and teak finish plinth 


£4.75 37p 


Duo Type I speakers (see opp. pagej 


£4.20 37p 


The above items purchased to gel her 


£25 £1 .50 



SOUND 50 

50 WATT AMPLIFIER & SPEAKER SYSTEM 




The ELEGANT SEVEN Mk. Ill 
(350m W Output) 

7 transistor fully-tunable M.W. — L.W. superhet 
portable. Set of parts. Complete with all com- 
ponents, including ready etched and drilled 
printed circuit board — back printed for foolproof 
construction. 
MAINS POWER PACK KIT: 47p extra. 

Price £5.25 plus 37p. P, & P. 
Circuit 13p FREE WITH PARTS. 



The 
^ DORSET 

(600m W Output) 



Price £5.25 
plus 37p P. & P. 

Circuit 13p 
FKEE WITH PARTS 



The Sound Fifty valve amplifier and speakers are sturdily 
constructed with smart housings and thoroughly tested 
electronics. They are designed to last — to withstand the 
knocks and bumps of life on the road. Built for the small 
and medium sized gig, they are easy to handle and quick 
to set up and can be relied upon to come over with all 
the quality and power you need. 

Output Power: 45 watts R.M.S. (Sine wave drive). Frequency response: 

-3dB points 30Hz at ISKHz. Total distortion: less than 2% at rated 

output. Signal to noise ratio: better than 60dB. 

Speaker Impedance: 3, 8 or 15 ohms. Bass Control Range: ± 13dB at 

60Hz. Treble Control Range: ± !2dB at 10 KHz, Inputs: 4 inputs at 

5mV into 470K. Each pair of inputs controlled by separate volume 

control. 2 inputs at 2Q0mV into 470K. 

To protect the output valves, the incorporated fail safe circuit will 

enable the amplifier to be used at half power. 

SPEAKERS! Size 20" x 20" x 10" incorporating Baker's 12* heavy 

duty 25 watt high flux, quality loudspeaker with cast frame. Cabinets 

attractively finished in two tone colour scheme — Black and grey. 



COMPLETE SYSTEM 

Sound 50 amp and 2 speakers 

or available separately. 

Amplifier £28.50 plus £1.50 P. & P. 

Speakers £12.50 each plus £1,75 P. & P. 



£50 



Plus 

£4 

P. &P. 



7- transistor fully tunable M.W. — L.W. super- 
het portable— with baby alarm facility. Set of 
parts. The latest modulised and p re-alignment 
techniques makes this simple to build. Sizes : 
12 x 8 x 3in. 
MAINS POWER PACK KIT : 47p extra. 




THE RELIANT Mk III 
SOLID-STATE GENERAL PURPOSE AMPLIFIER 

in simulated teak case £7.25 plus P. & P. 37p 

SPECIFICATIONS 

Output ± 10 watts. Output impedance— 3 to 4 ohms. 

Inputs 1. -xtal raic lOmV Tone Controls — Treble control range ± 

12dB at lOKHz. 2. -gram/radio 250mV. Bass control range ± 13dB 

at 100Hz. 

Frequency Response — (with tone controls central) Minus 3dB points 

at 20Hz and 40KHz. Signal to Noise Ratio — better than -60dB. 

Transistors — 4 silicon Planar type and 3 Germanium type. Mains 

input— 220/250V. A.C. Size of chassis— lOiin. x 4tin. x 2*in. For use 

with Std. or L,P. records, musical instruments, all makes of pick-ups 

and mikes. Built and tested. 



THE DUO SPEAKER SYSTEM 

Similar in design to those on the previous page the 2-way speaker 

system is beautifully finished in polished teak veneer. It is ideal for 

wall or shelf mounting either upright or horizontally. 

Type I SPECIFICATION :— 

Impedance 8 or 10 ohms (please state requirement'). It incorporates 

high flux 7in. x 3$in, speaker and 2Jin. speaker, Teak finish llfin. 

x 6in. x 5iin. £4.20 each. 37p P. & P. 



LIQUIDATED STOCK 



Uflftffl 



TOURISTE MK3 

CAR RADIO 



ALL TRANSISTOR 

Beautifully designed to blend with the interiors 
of all cars. Permeability tuning and long wave 
loading coils ensure excellent tracking, sensi- 
tivity and selectivity on both wave bands. R.F. 
sensitivity at 1 MHz is better than 8 micro volts. 
Power output into 3 ohm speaker is 3 watts. 

Originally sold completely builtfor£15.4.6 (£15.23) 
Pre-aligned I.F. module and tuner together with 
comprehensive instructions guarantees success 
first time. 12 volts negative or positive earth. 
Size 7in x 2in x 4£in deep. 

See top of previous page for address 




SET OF PARTS 

£6.30 

plus P. & P. 37p. 

Circuit diagram 13d. Free with parts 

Speaker, baffle and fixing kit 
£1.25 extra plus 20p. p. & p. 
Postage free when ordered with 
parts. 



R+TV 



1073 




the world's most advanced high fidelity modules 



Sinclair Project 60 presents high 
fidelity in such a way that it meets every 
requirement of performance, design, 
quality and value and now that the e- 
markabie phase lock loop stereo FM 
tuner is available, it becomes the most 
versatile of high fidelity systems. With 
Project 60, it is possible to start with a 



modest mono record reproducer and 
expand it to a sophisticated stereophonic 
radio and record reproducing system of 
fantastically good quality to hold its own 
with any other equipment, no matter how 
expensive. Project 60 is a unique high 
fidelity module system where compactness 
and ease of assembly are combined with 





System 


The Units to use 


together with 


Cost of Units 


A 


Simple battery 
record player 


Z.30 


Crystal P. L)„ 1 2V battery 
volume control 


89/6 
(£4.471) 


B 


Mams powered record 
player 


Z.30, PZ.5 


Crystal or ceramic P.U. 
volume control etc. 


£9.9.0 

(£9.45) 


C 


20+ 20 W. R. M.S. stereo 
amplifier for most needs 


2 x Z. 30s, Stereo 60, 
PZ.5 


Crystal, ceramic or mag, 
P.U, most dynamic 
speakers, P.M. tuner etc. 


£23.18.0 

(£23.90) 


D 


20+20W.R. M.S. stereo 
amplifier with high 
performance spkrs. 


2xZ.30s, Stereo 60, 
PZ.6 


High quality ceramic or 
magnetic P.U., F.M. Tuner, 
Tape Deck, etc. 


£26.18.0 

(£26.90) 


E 


40+40 W.R.M.S. de- 
luxe stereo amplifier ■ 


2 xZ. 60s, Stereo 60 
PZ.8, mainstrsfrmr 


As for D 


£32.17.6 

(£32.87*) 


F 


Outdoor P. A. system 


Z.50 


Mic, up to 4 P. A. speakers 
controls, etc. 


£5.9.6 
(£5.47J) 


G 


Indoor PA. 


Z.SO, PZ.8, mains 
transformer 


Mic, guitar, speakers, etc.. 
controls 


£17.8.6 

(£17.424) 


H 


High pass and low pass 

filters 


A.F.U. 


C.DorE 


£6.19.6 
(£5.974) 


J 


Radio 


Stereo F,M, Tuner 


C, D or E 


£25.0.0 



circuitry that is far in advance of any other 
manufacturer in the world. Thus it is 
extraordinarily easy to assemble any 
combination of modules using nothing 
more complicated than the simplest 
of tools, and you certainly do not have 
to be experienced to build with complete 
confidence. Tne 48 page manual free 
with Project 60 equipment makes every- 
thing easy and you can house your 
assembly in an existing cabinet, motor 
plinth, free standing cabinet or virtually 
any arrangement you wish. Once you 
have completed your assembly you will 
have superlatively good equipment to 
give you years of service and enjoyment. 
You will have obtained superb value for 
money because Project 60 is the best selling 
modular system in Europe and can there- 
fore be produced at extremely competitive 
prices and with excellent quality control. 

Sinclair Radionics Ltd.. London Road, St. Ives, 
Huntingdonshire PE1 7 4HJ. 
Tel: St. Ives (048 06) 4311 

sincdair— 



1074 



Sinclair Project 60 



fife 



Z.30 & Z.50 
power amplifiers 




The 2.30 and Z.50 are of advanced design 
using silicon epitaxial planar transistors to 
achieve unsurpassed standards of performance. 
Total harmonic distortion is en incredibly low 
0.02% at full output and all lower outputs. 
Whether you use Z.30 or Z.50 amplifiers in your 
Project 60 system will depend on personal 
preference, but they are the same size and may 
be used with other units in the Project 60 
range equally well. 

SPECIFICATIONS (Z.50 units are inter- 
changeable with Z.30s in aii applications). 

Power Outputs 

Z.30 15 watis R.M.S into 8 ohms using 35 volts: 
20 watts R.M.S into 3 ohms using 30 volts, 
Z.50 40 watts R.M.S. into 3 ohms using 40 volts: 
30 watts R.M.S. into 8 ohms, using 50 volts 
Freq u ancy response : 30 to 300, 000 Hz ± 1 d B 
Distortion : 02% into 8 ohms 
Signal to noise ratio: better than 70dB un- 
weighted. 

Input sensitivity: 250mV into 100 Kohms. 
For speakers from 3 to 1 5 ohms impedance. 
Size3ix2ixJ in. 
Z.30 

Built, tested and guaranteed with circuits and 
instructions manual 89/6 (£4 47-M 

Z.50 

Built, tested and guaranteed with circu-ts and 
instructions manual 109/6 ( £ 5 . 4 7 i ) 



Power Supply Units 




Designed specially for use with the Project 

60 system of your choice. 

Illustration shows PZ.5 to left and PZ.8 (for use 

with Z.50s) to the right. Use PZ.E for normal 

Z.30 assemblies and PZ.6 where a stabiised 

supply is essential. 

PZ-S 30 volts unstabiliseo '£4.19.6 (£4.97£) 

PZ-6 35 volts stabilised £7.19.6 (£7.9?i) 

PZ-8 45 volts stabilised 

(less mains transformer) £5.1 9.6 (£5.974) 

PZ-8 mains transformer £5 .1 9,6 (£5.971) 

Guarantee 

If within 3 months of purchasing Project 60 
modules directly from us. you are dissatisfied with 
them, we will refund your money at once. Each 
module is guaranteed to work perfectly and should 
any defect arise in normal use we will service it at 
once and without any cost to you whatsoever 
provided that it is returned to us within 2 years of the 
purchase date. There will be a small charge for 
service thereafter. No charge for postage by 
sutface mail. Air- mail charged at cost 



Stereo 60 
pre-amp/control unit 




j0» 



Designed for the Project 60 range but suitable 
for use with any high quality power amplifier. 
Again silicon epitaxial planar transistors are 
used throughout, achieving a realiy high 
signal-to-noise ratio and excellent tracking 
between channels. Input selection is by means 
of push buttons and accurate equalisation is 
provided for all the usual inputs. 

SPECIFICATIONS 

Input sensitivities: Radio-up to 3mV. Mag. p.u. 

3mV:correcttoR.I,A.A.curve± 1dB:20to25.000 Hz. 

Ceramic p. u.-up to 3mV: Aux-upto3mV. 

Qutput:250mV. 

Signal-to-noise ratio: better than 70dB. 

Channel matching: within IdB. 

Tone controls: TREBLE I- 15 to — 15dB a: 

fOKHz: BASS -,■ 1 5 to— 1 5dB at 100Hz. 

Front panel: brushed aluminium with black knobs 

and controls. 

Siie: 8ixHx4 ins. 

Built, tested 

and guaranteed. £9.19.6 (£9.97£) 

Active Filter Unit 




For use between Stereo 60 unit and two Z.30s 
or Z.50s. and is easily mounted. It is unique in 
that the cut-off frequencies are continu- 
ously variable, and as attenuation in the 
rejected band is rapid (12dB/octave). there is 
less loss of the wanted signal than has 
previously been possible. Amplitude and 
phase distortion are negligible. The A.F.U. is 
su itable for use with a ny other ampli fi er system. 
Two stages of filtering are incorporated — 
rumble (high pass) and scratch (low pass). 
Supply voltage - 15 to 35V. Current - 3mA. 
H.F. cut-off (~3dB) variable from 28k Hz to 
5kHz. L.F cut-off (-3dB) variable from 25Hz 
to 100Hz. Distortion at 1kHz (35V. supply) 
0.02% at rated output. 
Built, tested 
and guaranteed £5.19.6 (£5.97J) 



Stereo FM Tuner 



first in the world to use the 
phase Jock loop principle 

Before production of this tuner, the phase lock 
loop principle was used for receiving signals 
from space craft because of its vastly improved 
signal to noise ratio over other systems. Now, 
for the first time, the principle has been 
applied to an FM tuner with fantastically good 
results. Other original features include varicap 
diode tuning, printed circuit coils, an I.C. in the 
specially designed stereo decoder and squelch 
circuit for silent tuning between stations. 
Sensitivity is such that good reception be- 
comes possible in difficult areas. Foreign 
stations can be tuned in suitable conditions 
and often a few inches of wire are enough 
for an aerial. In terms of a high fidelity this 
tuner has a lower level of distortion than any 
other tuner we know. Stereo broadcasts are 
received automatically as the tuning control is 
rotated, a panel indicator lighting up as the 
stereo signal is tuned in. This tuner can also be 
used to advantage with any other high fidelity 
system. 

SPECIFICATIONS: 

Number of transistors: 15 plus 20 in I.C. 

Tuning range : 87.5to 1 08 M Hz. 

Capture ratio: 1.5dB 

Sensitivity: 2jiV for 30dB quieting: 7fjV for full 

limiting. 
Squelch level: 20m V. 
A.F.C. range: ±200 KHz 
Signal to noise ratio: >65dB 
Audio frequency response: 10Hz— 15KHz 

(±1dB) 
Total harmonic distortion: 0,15% for 30% 

modulation 
Stereo decoder operating level : 2uV 
Pilot tona suppression : 30dB 
Crosstalk: 40dB 
I. F. frequency: 10.7 MHz 
Output voltage : 2 x 1 50mV R.M.S 
Aerial Impedance: 75 Ohms 
Indicators : Mains on: Stereo on; tuning indicator 
Operating voltage: 25-30 VDC 
Size ; 3.6 x 1 .6 x 8.1 5 inches: 91 .5 x 40 x 207 mm 



L — Lj — ] r ~^n_LCT 



Price: £25 builtand tested. Post free 



To: SINCLAIR RADIONICS LTD LONDON ROAD ST. IVES HUNTINGDONSHIRE PE17 4HJ 



Please send 



for which I enclose cash/cheque/money order. 



Name 



Address 



PW.471 



1075 



Sinclair IC10 Q16 Micromatic 




The world's most advanced high 

fidelity amplifier 

This is the world's first monolithic integrated 
circuit high fidelity power amplifier and pre- 
amplifier. The circuit itself is a chip of silicon 
only a twentieth of an inch square by one 
hundredth of an inch thick, having 5 watts 
RMS output (10 watts peak). It contains 13 
transistors (including two power types). 2 
diodes. 1 zener diode and 18 resistors, and is 
encapsulated in a solid plastic package which 
holds the metal heat sink and connecting pins 
This exciting device is more rugged and has 
considerable performance advantages, in- 
cluding complete freedom from thermal 
runaway and a very low level of distortion. 
The IC10 is primarily intended as a full 
performance high fidelity power and pre- 
amplifier, for which application it only 
requires the addition of such components as 
tone and volume controls and a batten/ or 
mains power supply. It may also be used in 
other applications including car radios, 
electronic organs, servo amplifiers (it is dc 
coupled throughout) etc. 
Circuit Description 

The first three transistors are used in the 
pre-amp and the remaining 10 in the power 
amplifier. Class AB output is used with 
closely controlled quiescent -current which is 
independent of temperature. There is generous 
negative feedback round both sections and 
the amplifier is completely free from crossover 
distortion at all supply voltages, making 
battery operation eminently satisfactory. 
Each IC10 is sold with a comprehensive 
manual giving circuit and wiring diagrams for 
a large number of applications in addition to 
high fidelity. These include oscillators, etc. 
The pre-amp section can be used as an RF or 
IF. amplifier without any additional transistors. 

Specifications: 

Output: 10 warts peak. 5 watts RMS continuous. 
Frequency response : 5 Hz to 100kHz 1 ± dB. 
Total harmonic distortion: Less than 1% at full 
output. 

Load impedance : 3 to 1 5 ohms. 
Power gain: 110 dB (100.000,000.000 times) 
total- 
Supply voltage : 8 to 18 volts, (A Sinclair power 
unit, PZ .7 is available for mains operation). 
Size: 1 x 0,4 x 0.2 in. plus neat sink and tags. 
Sensitivity 5 mV. 

Input impedance: Adjustable externally up to 
2.5 Mohms. 
Price (with manual): 53/6 (£2.97±) post free. 



Q16 



VJicromatic 




High fidelity loudspeaker 

The Q1 6 employs the well proven acoustic 
principles specially developed by Sinclair in 
which a special driver assembly is meticulously 
matched to The characteristics cf the uniquely 
designed cabinet. In reviewing this exclusive 
Sinclair design, technical journals have justly 
compared the Q1 6 with much more expersive 
loudspeakers. Its shape enables the 01 6 to be 
positioned and matched to its environment to 
much better effect than is the case with 
conventionally styled enclosures. A solid tea?; 
surround with a special all-over cellular foam 
front is used as much for appearance as its 
ability to pass all audio frequencies. 

This elegantly designed shelf mounting 
speaker brings genuine high fidelity within 
reach of every music lover. 



Specifications : 

Construction : Special sealed seamless sound or 

pressure chamber with internal baffle. 

Loading: up to 14 watts TMS. 

Input impedance: 8 ohms. 

Frequency response: From 60 10 16,000 Hz, 

confirmed by independently plotted B and K cu've. 

Driver unit: Special high compliance unit having 

massive ceramic magnet of 1 1 .000 gauss, aluminium: 

speech coil and a special cone suspension for 

excellent transient response. 

Size and styling : 9f in square on face x 41 in. deep 

with neat pedestal base. Black all-over cellular foam 

front with natural solid teak surround. 

Price f 8.1 9.B,(E8.B7i). 



To: SINCLAIR RADIONICS LTD LONDON ROAD ST. IVES HUNTINGDONSHIRE PE17 *HJ 
Please send Name 



Address 



for which I enclose cash/cheque/money order. 




Britain's smallest radio 

Considerably smaller than an ordinary box of 
matches, this is a multi-stage AM receiver 
brilliantly designed to provide remarkable 
standards of selectivity, power and quality for 
its size. Powerful AGC counteracts fading 
from distant siations: bandspread at higher 
frequencies makes reception of Radio 1 easy. 
The plug-in magnetic earpiece provided 
matches the Micromatic 's output to give 
wonderful standards of reproduction. Every- 
thing including the special ferrite rod aerial and 
batteries is contained within the minute and 
attractively designed case. Whether you build 
a Micromatic kit or buy this amazing receiver 
ready built and tested, you will find it as easy 
to take with you as your wrist watch, and 
cependable under the severest listening 
conditions. 

Specifications: 

Size: 36 x 33 x 13 mm (1^/s x l 3 /io * t in.) 

Weight: mcludng batteries, 28.4 gm (1 oz). 

Case : Black plastic with anodised aluminium front 

panel and spun aluminium dial. 

Tuning: medium wa^e band with bandspread at 

higher frequencies. (550 to 1,600 Hz). 

Earpiece : Magnetic type. 

On/off switching : By inserting and withdrawing 

earpiece plug. 

Kit in pack with earpiece, case, instructions and 

solder 49/6 (£2.47*). 

Ready built, tested and guaranteed, with earpiece 

§S/t(£Z97«. 

Two Mal/ory Mercury batteries type HM675 

required. From radio shops, chemists, etc. 



Sinclair Radionics Ltd.. London Road. 
St. Ives, Huntingdonshire PE17 4HJ. 
Tei: St. Ives (048 06) 4311 



lair- 



1076 




TptANGE OF SOLID STATE 
Jen... MAINS AMPLIFIERS 

"I" 1 ' 1 "" ii U mt niJ Employing only 
high grade components and transistors. 




£11 



Recommended 

Retail price 

Size 9ix21x5im. Appro*. 

Controls (5) Volume, Bass 

Treble. Mains Switch, Input 

Selector Switch. 



LT55 6 WATT 
AMPLIFIER 

A HIGH FIDELITY UNIT PRO- 
VIDING EXCELLENT RESULTS 
AT MODEST OUTPUT LEVELS. 



Sensitivity 5 mv (max). 

Frequency Response 30-20,000 cps — 2dB 

Harmonic Distortion 0.5% at 1,000 cps 

Output Rating I.H.F.M. 6 Watt 

Input Sockets for "Mike," Gram and 

Radio Tuner/Tape Recorder. 

Suitable for speakers 3-15 ohms. 



LT66 12 WATT 
STEREO AMPLIFIER 

A TWIN CHANNEL VERSION 

OF THE LT5S PROVIDING 

UP TO 6 WATTS I.H.F.M. 

HIGH FIDELITY OUTPUT ON 

EACH CHANNEL. 

Switched Input Facilities 

Socket (1) Tape or crystal PU Recommended 

(2) Radio Tuner (3) Ceramic PU Retail price 

Microphone. Size 12 x 3 1 x 6m. Approx. 

Controls (6) Volume, Bass, Treble, Balance, Mains Switch, Input Selector 
Switch, Stereo /Mono Switch. 

Facia Plate Rigid Ferspex with black /silver background and matching 
black edged knobs with silver finish centres. 




£21 



It required an attrac- PLEASE SEND A STAMPED ADDRESSED ENVELOPE 
tlve vood cabin ft with I FOR FULL DETAILS OF ABOVE UNITS 

veneer finish can be 

ropplted for any model J AVAILABLE FROM YOUR LOCAL HI-FI DEALIR 

Prices From £3.50 Wholinit end Rttall tnqutrlti to: 



LINEAR PRODUCTS LTD, Electron Works, Armley, Leeds 



P.W. COMMUNICATIONS RECEIVER 

(P.W. DEC. '70) 

Was built entirely from parts supplied by us. 
Kits of parts exactly to spec : — 

2nd Convertor/I.F. Kit £7.90 

Product Det. (with V/C) £2.90 

Audio Amp £1.80 

Pre Sel./1 st Con £5.50 

Power Supply £2.50 

COMPLETE KIT All of above plus sub chassis 

material and F/T capacitors .... £20.00 
OTHER W, CAMERON DESIGNS 

F.M. Tuner (Feb. 1969) £8.20 

F.M. Stereo Decoder (May 70) £4.80 

Stereo Amp (Dec.-Feb. '68). S.A.E. for list. 

Post and packing per order 15p (Post free on complete kits) 
C & D ELECTRONICS 
1, Neville Road, St. Lukes Cross, Sunderland 





ME 


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■ Guaranteed an 


d Tested 


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.W V 


ALVto 


■ 24-HOUR SE 


RVICE 


IBB 


87 


30PL14 -87 


EBC33 


S3 F.L33 


■IS 


FCF805 


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B19 -SI 


ISO 


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OCH35 


•85 


EBF89 


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ELS4 


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PCF806 


68 


TJ2B 


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DAC32 


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EOC81 


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FCL82 


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TJ191 


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PCL85 


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TJ261 


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KT81 


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DF96 


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ECH35 


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EF39 


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PL500 


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M 




Postage or 


1 valve iiii 


on 2 o 


r more valv 


ea 3p per valve 


extra. Any pan 


tef insnred against 


damage in 


■tw 


null 3p 


extra. 


Office add i 


ess. 


no callers. 













GERALD BERNARD 

83, OSBALDESTON ROAD, STOKE NEWiNGTON, LONDON, N.16 



fifll 



N*»S^2 



■^ 



Jc- PORTABLE MAINS 

FULLY TRANSISTORISED 

MINI -TELE 



127 

screen! 



3§£5 

BBCl. 

BBC2,and (TV. 
* Brilliant 625 lines 

picture. 
*Full after sales service 
*12 months written guarantee. 



QNLV x5rS7p $4j -t 



First Class Makers— We Must Not Mention Name! 

THIS OFFER ONLY FROM US! Due to Shopertunltle*' sensational scoop 
purchase of entire advance shipment for caah not only do you get this fabulous, 
brand spanking new 1971 model, fully trans lit or Ised, portable/ mains, 625-line TV 
with BIG 12" SCREEN wall ahead of everyone elsa but you SAVE £31.50 AS 
WELL I Even If you've got the b loo est, most expensive colour TV already — you'll 
love this I And at our amazing price you could even afford to buy one aa a second 
setl Brilliantly designed Incorporating the very latest techniques and refine* 
mentsl Beautifully made and finished. Superb pert or mane a I Carry It from room to 
room ss desired, simply plug In — no wafting, no "warming-up," no old fashioned 
outside aerials — perfect sound and crystal clear vision almost Instantly] Control 
sound from a whisper to a roar — no Image refection, even on maximum volume I 
Full range of simple controls. Extra smooth station selection dial. Siie overall 
approx. «r X H" X 11 i". Weight 1»4lbs approx. 220 240 v AC. Yea, only £61.97 
carr, etc. £1. (Certified guarantee sent with every set.} No more to pay] This fantastic 
offer may never be repeated — so why not get two or more, while the going's good 7 
Get one for grandma) Get one for the children] Get one for the bedrooml Get one 
as a gift] At Shoperfunltles Incredible price you just can't loael Send or call. 






%aift~~~~^ 



°W 



6 WAVEBAND 



; WORLDWIDE: 

' THOUSANDS Of TRANSMISSIONS. ' 
- APBSTATlOaSTKEWORiOOVER! ' 



10 TRANSISTOR [3j 

PLUS 3 DIODES (4~; 

PORTABLE RADIO £§ 

£9-97 E 

» BOX posrrrc. 43m j**" 



) 



NOT JUST A RADIO-BUT TECHNOLOGICAL MAGIC! 



^COMPARE 

ITS KftKlr»IAMCE with 

£34 RADIOS' 



What everyone's been watting for— THE LATEST 1171 

MODEL, SUPERSEDING ALL PREVIOUS MODELS ;- 
THE FANTASTIC BRAND NEW RUSSIAN "MERI- 
DIAN" B-WAVEBAND PORTABLE RADIO. DE- 
SIGNED FOR WORLD WIDE RECEPTION. Only 

finally put Into production after Incorporation of every conceivable possible 
up-to-date technological Improvement had been carefully considered and 
thoroughly examined. So advanced It will probably make your present radio 
seem like a "crystal set"! It's far better than any o-wsve radio even they have 
produced! Finest value we've ever offered! we're almost giving them away at 
£9.97 — a mere fraction of even to day 'a Russian miracle price) We challenge 
you to compare performance and value with that of £34 radios! *You can't lose. 
Instant refund if you are not astounded! Purer and sweater tone than ever I Much 
wider band spread than hitherto for "pin-point" station selection 1 Once again 
the Russians have proved their fantastic ability in the field of electronics— brilliantly 
reflecting their advanced micro-circuitry techniques In the field of spaceship and 
satellite communications. YOU GET THIS AMAZING SET FROM US AT A PRICE 
THAT BEARS NO RELATION TO ITS TRUE VALUEI Yes. • separata wavebands, 
Including Standard Long, Medium and Short Waves to cover the world! 
Unique side control waveband selection unit gives Incredible esse of station 
tuning I Thousands of different transmissions and stations at your fingertips 

24 hours a day, even ships at sea and messages from all over the world nothing 

ia secretl The radio enthusiast can have the world In the palm of his hand! 
Superb, sweet tone— controlled from a whisper to a roar that will fill a hall! Genuine 
push-pull output! Separate ON /OFF volume end Treble 'Bass tone controls! Take 
It anywhere — runs economically on standard batteries. Internal ferrlte rod aerial 
plus built-in telescopic aerial extending to full 33 T ln. length. It's also a fabulous 
CAR RADIO— any spaed, requires no additional aerial. UNIQUE! Elegant 
Black, White and Chrome finish case. SIZE lW"x 8" x 34" overall approx. Magnifi- 
cently designed and made to give yean of perfect service. With WRITTEN 
GUARANTEE, manual with slmpte operating Instructions and circuit diagram. 
ONLY £9.97. POST ETC., «p. Standard batteries tip extra. Can also be used 
through extension amplifier, tape recorder or public address. Send or call. 

tmaBBSBBBESSSSn ttEl D " p '- Wi>/ *' 1M u xbr,d g e road. 

s t- u. h s ^h i. ju iii , tJ T i f^ L -^ J {fac|ng 5hwh , rd ., Bu , n Green), 

LONDON, W1Z SAQ (Thurs. 1, Fri, 7). Also 37 High Holborn, London. W.C.t 

(Wed. 1, Thurs. 7). Both stores open from MON.-SAT. from 9 a.m. until 6 p.m. 

1077 



HI-PI DISCOUNT 



DRIVE-IN CAR PARK 




Rec. Retail Comet 

Price Price 

STEREO AMPLIFIERS 

ARMSTRONG 521 56 00 44 50 

DULCI 207 25 00 17 M 

•DULCt 207M 30-00 MOO 

FERROGRAPH F307 5900 480* 

GOODMANS Maaamp 54-00 38 00 

LEAK Stereo 30 Plus 58-60 44-75 

LEAK Stereo 30 Plus, In teak case 62 50 49 59 

LEAK Stereo 70 60-00 5500 

LEAK Stereo 70, In teak case .... 75-00 50-50 

•LINEAR LT 68 21-00 17-00 

METROSOUND ST2Q :..., 3600 28-00 

PHILIPS RH 591 76-75 58 00 

PHILIPS RH 590 51-75 39-50 

PHILIPS RH 580 2800 22 00 

PIONEER SA500 62-10 43 00 

PIONEER SA700 98-00 7000 

PIONEER SA900 134-10 9700 

PIONEER Reverberation 45-50 3300 

ROGERS Ravensbourne ...... 59-50 47 00 

ROGERS Ravensbourne (cased) .. 6400 50-00 

ROGERS Ravensbrook Mk. II .... 47-50 38-00 
ROGERS Havenebrook (cased) 

Mk.ll 52-50 42 00 

•SINCLAIR2000 30-45 23-00 

SINCLAIR PROJECT 60/2 X Z3Q< 

PZ5 23-90 17 00 

SINCLAIR PROJECT 60/2 X Z50/ 

PZS/trans 32-88 23-50 

SINCLAIR Neoteric 61-95 48-00 

SINCLAIR 3000 4500 3800 

TELETON 203E 28- 75 2000 

TELETON GA 101 30w RMS 37-50 28-50 

VOLTEX 100w. Stereo Discotheque, 

8 electronically mixed inputs 185-00 13900 

Starred Items above take ceramic cartridges only. 

All others lake both ceramic and magnetic cart- 
ridges. 



TUNERS 

•ARMSTRONG 523 AM/FM 53-76 4500 

•ARMSTRONG 524 FM 41-89 3100 

ARMSTRONG MB Decoder 9-50 800 

•DULCI FMT.7 FM 22-05 18-00 

DULCI FMT.7S Stereo 31-00 25-25 

GOODMANS Stereomax 82-52 49-95 

LEAK Stereofetlc Chassis 66-50 52-00 

LEAK Stereotetic in teak case .... 72-50 59-00 

PHILIPSRH690 44-50 35-50 

PHILIPS RH 691 89-00 7550 

PIONEER TX50QAMfFM 77-94 04 00 

PtONEERTXOOO AM/FM 15369 125 90 

ROGERS Ravens bourne 61-89 50-00 

ROGERS Ravensbrook 45-01 40-00 

ROGERS Ravensbrook (cased) 51-26 4300 

•SINCLAIR 2000... 26-73 19-25 

SINCLAIR Project 60 25-00 2100 

TELETON GT 101 ,. 45-50 3400 

TELETON 201 X FM 36-00 30-00 

All above Tuners are complete with MPX Stereo 
Decoder except where starred. 



TUNER AMPLIFIERS 

AKAI6600 142-53 112 00 

ARENA R500 8200 9700 

ARENA 2400 90-30 72-00 

ARENA 2600 Stereo AM/FM 111-30 94 00 

ARENA 2700 10500 8500 

ARENA T1500F 72-45 6000 

ARENA T9000 303-45 258-00 

ARMSTRONG M8 Decoder 9-50 800 

ARMSTRONG 625 91-89 7700 

ARMSTRONG 526, 104-71 87 00 

GOODMANS 3000 , 77-73 5300 

•PHILIPS RH 781 74-98 5500 

PHILIPS RH 790 13500 1*9 00 

PIONEER KX330 AM/FM/SW .... 7862 93-00 

PIONEER SX770 AM/FM 160-43 128 00 

PIONEER SX990 AM/FM 194-74 150 00 

•TELETON F2000 51-50 32-00 

TELETON 7 AT 20 10500 8000 

TELETON 10AT1 150w. RMS 160-00 109 00 

TELETON TFS50 75-50 58-00 

•TELETON R.8O00 with Speakers 63-25 50-00 

TELETON CR55 12000 9500 

WHARFEDALE 100.1 131-25 105 00 

Starred Items above take ceramic cartridges only. 
All others take both ceramic and magnetic cart- 
ridges. 

All the above Tuners and Tuner,' Amplifiers include 
MPX Stereo Decoder with the exception of Arm- 
atrong where decoder Is extra as listed. 




PICKUP ARMS 

GOLDRING Lenco L75 12-33 10-50 

COLORING Lenco L69 929 7-08 

SME 3009 with S2 Shell .......... 31-31 28-00 

SME 3012 with 52 Shell 33-35 29-00 

CARTRIDGES 

GOLDRING 800 13-00 7-50 

GOLDRING 800H 10-69 8-00 

GOLDRING 800E 18-88 12-25 

GOLDRING 800 Super E 26-01 2000 

•GOLDRING C590 Stereo 5-20 423 

•GOLDRING CS9VE 7-81 6-2S 

GOLDRING G850 6-50 5 25 

EMPIRE 1Q0ZE/X 6300 52 50 

EMPIRE 999VE/X 44-50 38 00 

EMPIRE 99BTE/X...... 27-60 22-50 

EMPIRE 999SE/X 21-00 17-50 

EMPIRE999E/X 16-50 13-00 

EMP1RE999/X 11-50 925 

EMPIRE 909EfX 12-85 10-25 

EMPIRE90BX 9'00 7-50 

EMPIRE 90EE/X 9-75 8 00 

ORBIT Magnetic NM 22 .... Special Price 2-90 

PICKERING VIS AC2 8-40 700 

ORTOFON SL15E 29-65 23-75 

ORTOFON 2X15K Transformer,... 7-00 8-25 

SHURE M3DM 7-41 5-25 

SHURE M31E 1205 8-50 

SHURE M32E 11-10 8-75 

SHURE M32-3 10-20 8 00 

SHURE M44-5 11-10 8-50 

SHURE M44-7 10-20 B-Ot 

SHUREM-44C 10-20 8-00 

SHURE M44E 12-05 9-50 

SHURE M55E 12-95 10-25 

SHURE M75G 17-60 14 90 

SHURE M75-6 16-70 13-00 

SHURE M75EJ .. 19-45 1(00 

SHURE M75E-95G 23-15 1804 

SHURE M7SE 21-30 16 00 

SHURE M75E/D19 23-15 1900 

SHURE V15-11 40-76 3080 

SHUREV15-11-7 38-90 2900 

Starred cartridges above are ceramic. All others are 
magnetic. 

TURNTABLES 

GARRARD SP2S, fully wired with Goldrlng 

6800 Magnetic Cartridge. Complete with 
base, plinth and cover — Special Price 20 98 

DUAL1219transcriptlon 50-40 50-00 

DUAL1209transcriptlOn 42-62 35 00 

GARRARD SP2S Mk III 16-45 11-99 

GARRARD SL65 B 21-25 15-90 

GARRARD SL75 B 3895 28-50 

GARRARD SL95 B 53-27 38-54 

GARRARD 401 3807 29-50 

GARRARD SL72 B 32-77 26-84 

GARRARD 3500, with GKS Cart- 
ridge 17-23 12-99 

Base and Cover to fit GARRARD 
SP25, SL55, SL65B and 3500 ..Special Price 400 

GARRARD 40B 13-84 10-87 

GARRARD AP 76 28-88 21-54 

GOLDRING 705/P with 850 Cart- 
ridge and Cover 26-00 23-90 

GOLDRINGGL69Mk.il 26-63 22-50 

GOLDRING GL69 P Mk. II 35-14 29-50 

GOLDRING GL75 36-41 33-90 

GOLDRING GL75 P 46-94 41-90 

GOLDRING Covers for 69P and 75P 4-21 3-50 
GOLDRING C99— plinth and cover 

forG99 11-45 8-94 

goldringg99 26-00 23-90 

goodmans 302s 37-74 26-90 

Mcdonald mp oo 15-75 12-25 



COMET for 

after -sales service 

THROUGHOUT THE U.K. 

Pictured, Service Dept 
at Clough Rd, Hull 
also at Leeds, Goole, 
Wakefield, Doncaster, 
and Bridlington 



Rec. Retail Comet 
Price Price 



Mcdonald 610 20-1 

Base and Cover for Mc DONALD 
MP 60 and 610 Special 



PHILIPS 228 20 

PHILIPS GA 146 31 ■ 

PHILIPS217 33' 

PHILIPS 202 Electronic 69 

PIONEERPL12A 50, 

PIONEER PL11 87' 

THORENS TX 25 cover 8' 

THORENS TD125 75' 

THORENS TD150A Mk. II 43' 

THORENS TD125AB 120' 

THORENS TD150AB Mk. II 47 

THORENS TX11 Cover 4 



1704 
2500 
28 00 
57-59 
39 95 
3900 

6-53 
82-00 
3304 
100 Q0 
41-04 

3-75 



SPEAKERS 

ARENA HT 16 

B4 W Model 70 

B A W DM3 

B i W OM1 

CELESTION Dltton 120 

CELESTION Dltton 15 

CELESTION Ditton 25 

GOODMANS Minister 

GOODMANS Magister 

GOODMANS Maxim 

GOODMANS Mezzo 3 

GOODMANS Magnum K2 

KEF Celeste 

KEF Concord 

KEF Concerto 

KEF Cresta 

KELETRON KN 654/3 3 speaker 



KELETRON KM 824 3 3 speaker 

system (pair) 

KELETRON KN 104/3 3 speaker 

system 

KELETRON KN 123/3 3 speaker 

system 

KELETRON KN 120/4 4 speaker 

system 

LEAK 200 

LEAK 300 

LEAK 600 

LOWTHER Acousta (with PM6) .. 
LOWTHER Acousta (with PM7) . . 

LOWTHER Ideal Baffle 

METROSOUND HFS 20 

PHILIPS RH481 

PHILIPS RH482 

SINCLAIR 016 

STE-MA 275 3 speaker system .... 
WHARFEDALE Speakers 

Airedale 

Denton 

Super Linton 

Melton 

Dovedale 3 

Rosedale 

Triton (pair) 

Unit 3 Speaker Kit 

Unit 4 Speaker Kit 

Unit 5 Speaker Kit 



00 



CHASSIS SPEAKERS 

GOODMANS Axiette S 7-46 

GOODMANS T«i I naxlette 8 8-44 

GOODMANS Axiom 10 8-84 

GOODMANS Axiom 80 2607 

GOODMANS Axiom 201. 13-45 

GOODMANS Axiom 301 19-25 

GOODMANS AudiomSP.. 5 50 

GOODMANS AudlomlOP 6-00 

GOODMANS Audlom 51 12-15 

GOODMANS Audlom 61 17-60 

GOODMANS 12P 1287 



10 95 
115 00 
53-00 
25 50 
18-00 
23-00 
4704 
1904 
4500 
18-75 
23-90 
29-90 
21 50 
33 00 
42-90 
1800 

14 97 

18 97 



18-97 
17-99 
23 50 
36 90 
38-50 
46 00 
30-00 

13 50 
9-25 

15-09 
8-00 
15 00 

56 00 
15-90 
20 50 
25-50 
32-50 
52-50 
46 90 
10-50 

14 25 
20 50 



00 I 

00 I 



1078 



(OVER 1,520 sq. yds.) 




OVER lOOO ITEMS 
ALWAYS IN STOCK 

ALL FULLY GUARANTEED - 
WITH AFTER-SALES SERVICE 

All items offered are brand new, latest models in manufacturers' sealed cartons 



Rec. Retail Comet 

Price Price 

GOODMANS 15P 2000 H-9T 

GOODMANS Audiom 1BP 3400 26-87 

GOODMANS Twin Axiom 10 .... 9-42 7 75 

GOODMANS ARU 172 3-Sfl 304 

GOODMANS Trebax 100 7'*5 5-JO 

GOODMANS Trebax SK/20XL .... 8-40 •-» 

GOODMANS Mldax 11-20 S-50 

GOODMANS Attenuator 3-07 2 IS 

GOODMANS Crossover Networks 

XO,'950/5O00 8*3 i 25 

GOODMANS Crossover Networks 

XQ/950 6-39 4-75 

GOODMANS Crossover Networks 

XO/5000 2-30 1-75 

WHARFEDALE S tn. Bronze/RS/ 

DD 500 400 

WHARFEDALE Super 8.R5/DD .. 8-50 700 

WHARFEDALE Super 10/RS'DD 14 00 11-50 
WHARFEDALE WMT 1 Matching 

Transformer 0-84 0-75 

LOW COST AUDIO SYSTEMS (complete) 

ALBA UA552 47-50 35-9* 

ALBA UA562 62-99 47-W 

ARENA MR 15 14500 11588 

BUSH System 7 49,740; 764 102 65 82-75 

DECCA Sound 603 72-50 I0-00 

DECCA Sound 604 72-50 6100 

DECCA Sound 1203 97-50 8000 

DECCALIAN 5 complete with 

stand 65-50 53 00 

EKCO S.R.G. 609 8850 70-00 

FERGUSON206S 117-00 1000 

FERGUSON 3422 84-70 69-00 

GOODMANS 3000 Suite 140-45 9600 

HMV 2416 128-70 105 00 

HMV 2404'5,-6 202-85 17000 

KB KA1250 7200 St -00 

KB KA1250651 83-00 61 98 

MARCONI Unit 4 77-45 67 00 

MARCONI Unit 3 85-00 70 00 

M ETROSO UN D Stereo 1010 77-32 66 00 

PHILIPSGF823 49-50 39 88 

PHIL5PSGP824 67-50 55 98 

PHILIPS RF 833 67-50 55-88 

PHILIPSRF834 8800 73-98 

TELETON B-track Stereo 52-25 4800 

TELETON C RIOT '2025/1003 with 

stereo radio 62-10 45-98 

TELETON CMS400 102-50 70-00 

TELETON 2S60F 7500 S6-00 

TOSHIBA SP8507 24800 18100 

ULTRA 6405 79-75 6708 

TAPE RECORDERS AND TAPE DECKS 
ALBA R22 Twin Track Battery/ 

Mains 50-25 24 W 

AKAIM10L 245-05 189 99 

AKAIX200O 190 00 160 00 

AKAIX5000W/L 177-98 140-00 

AKAl X330 342-57 269 00 

AKAIX-330D 312-56 24500 

AKA I X-360 .,...:. 38008 28400 

AKAl X-360 O-deck 318 92 24300 

AKAM8O0SD 199-42 18700 

AKAl 1710L 89-85 *8 90 

AKAl CR80 B-track stereo recorder 11503 99 98 
AKAl CR80D B-track stereo tape 

deck 95-00 79 98 

AKAl 4000 4-track Stereo 124 90 1O0O0 

70*0 



AKAl 4000 D 4-track Stereo deck 

BUSH TP 60 Cassette Tape Re- 
corder 

BUSH TP 70 Cassette Battery/ 
Mains Tape Recorder 

BUSH discassette DC70 

FERGUSON 3244 Stereo 4-track .. 

FERGUSON 3245 Twin track .... 



33 SB 

29-40 25 00 



29-95 
19-95 
97-90 
3705 



24 00 
14-98 

80 00 
3000 



Roc. Retail Comet 

Price Price 

FERGUSON 3246 4-track 43 00 34-00 

FERGUSON 3247 4-track 48-45 3900 

FERGUSON 3248 4-traek 54-30 4200 

FERGUSON 3249 4-track 64-30 5000 

FERROGRAPH 722 242-54 199 00 

FERROGRAPH 724 242-54 189-00 

FERROGRAPH 702/W 2 track tape 

deck 207-35 17500 

FERROGRAPH 704/W 4 track tape 

deck 207-35 17500 

GRUNOIG C200L Cassette 39-90 3000 

GRUNDIG TK 141 (4-track) 61-85 5000 

GRUNDIG TK 121 (Twin-track) .. 66-85 44-00 

GRUNDIG TK 146 (4-track Auto) ,. 68-14 53-98 

GRUNDIG TK 12+ Twin-track .... 44-90 35-00 

GRUNDIG TK 149 4-track 57-64 48-00 

PHIL1PS2202 29-90 24 00 

PHILIPS 2205 Cassette Tape 

Recorder 43-15 34 98 

PHI LIPS 4404 4-track stereo recorder 95 00 73-9* 

PHILIPS 4407 4-track stereo recorder 110 00 89-88 

PHILIPS 4302 Twin Track Auto .. 39-00 3200 

PHI LIPS 4307 4-track 49-50 3900 

PHILIPS 4500 4-Traek Stereo Tape 

Deck 12600 99-00 

PHILIPS 4408 4-Track Stereo .... 13900 109 00 

PHI LI PS N4404 4-Traek Stereo .... 83 ■ 00 TO ■ 00 

PHILIPS N4308 60-50 5000 

PYE Cassette Recorder/Radio (Batt. 

/Mains) 45-50 3700 

TELETON FXB 510 D 4-track Stereo 62-50 48 00 
TELETON 5L40 Twin Track Battery/ 

Mains 

TELETON TRC 130 cassette, with 

VHF AM radio battery/mains twin 

motors 

TELETON TC110 cassette battery/ 

mains 27-50 19 -98 

TOSHIBA GTB40S 110-00 WOO 

TOSHIBA GT 601v Twin Track .. 4S-15 300* 

TOSHIBA 850 SA 94-00 60 00 

BASES AND COVERS 

GARRARD WB1 Base.. 

GARRARD WB4 Base 

GARRARD SPC 1 Cover ... 
GARRARD SPC 4 Cover ... 



38-50 25 00 



39-50 29 -98 



3-86 
5-69 
3-74 
4-44 



3-25 

4-75 
3-00 
3 75 



SPECIAL OFFER OF BASE AND COVER TO FIT 
GARRARD SPSS, SL5S, SL65B and 

3500 Special Price 4 00 

GOLDRING Plinth 75 8-52 7-tO 

GOLDRING Plinth 69 8-52 7 0* 

GOLDRING Covers for 69P and 75P 4-21 3 50 
THORENS TX25 (for TD125AB) .. 8-22 6 5* 

THORENS TX11 Cover 4-11 3-75 

Base and Cover for TD 125 15-18 12-5* 

SME Plinth System 2000 39-20 31-25 

MOTORBOARDS only 495 300 

HEADPHONES 

AKAl 6-50 5-25 

AGK K60 13-50 10-75 

KOSS ESP-9 Electrostatic 69-00 5350 

KOSS ESP-6 Electrostatic 4500 36*0 

KOSS PRO-4AA 2800 22 5* 

KOSS PRO-4A 2300 IBS* 

KOSS KO-727B 16-50 13-50 

KOSS K-6........ 12-60 9-95 

KOSS SP-3XC 9-50 7-50 

MIDLAND SH700 Special Price 3 95 

SHRIRO Special Price 400 

TELETON..... 5-00 3 25 



Rec. Retail Comet 
Price Price 



Open daily to 
the public from 
9-0 A.M. until - 

5-30 P.M. MOM. 
1-0 P.M. TUES. 
8-0 P.M. WED. 
8-0 P.M. THUR. 
8-0 P.M. FRI. 
5-30 P.M. SAT. 

Customers are 
welcome to call - 
Ample car parking 

facilities 



TEAK CASES 

Leak 70/30 Amp. case 7-17 6 25 

Leak Tuner case 7-17 6 25 

Leak Double case for amp. A tuner 9-93 150 

Complete Price List FREE on request! 

C^H^i^f'HIGH FIDELITY 

DISCOUNT WAREHOUSES 

Reservoir Rd., Clough Rd., Hull HU6 7QD £|S8B 
68 A Arm ley Rd. (Artist St) Leeds LS12 2EF 5 e ,S s 
Teesway, Portrack Lane, North Tees Side isms*" 2 
Industrial Estate KTS 18 2RH Tees Side. K,,n6 " 

(SerWce Dent., New Road Side, Horsfarth, Leeds) 
Comet guarantees that all prices quoted are genuine. All Items offered 
available at these prices at the time this Issue closed for press. 
Add 75p for post, packing and Insurance on all orders (Cartridges 20p) 

or, if Securicor delivery required, add £1.50 only. 

Make cheques, Money Order* payable to "COMET". 



COMPLETE HI-FI 
SYSTEMS 

Completely wired, mounted and 
ready for use 



TELETON Stereo 6 track tape Audio 
system complete 52 25 46-00 



GARRARD SP 25, mounted In 
base, plinth and cover with 
GOLDRING G300 Cartridge. 
Teleton 203 Stereo Amplifier 
12 watts RMS, and 2 KELETRON 
654/3 Speakers, each speaker Is a 
2 speaker system 84-33 SIM 



GOLDRING GL69PML 11 mounted 
In base with hinged lid, GOLD- 
RING G800 Cartridge, Rogers 
Ravensbrook Amplifier In Teak 
case. Two Wharfedale Super 
Linton Speakers 151-25 115 05 



GOLDRING GL 75P mounted In 
teak base with hinged perapex 
cover complete with GOLDRING 
G800E Cartridge. Leak Stereo 30 
Plus Amplifier In Teak case. 2 
GOODMANS Mezzo 3 Speakers 194 30 14! 00 



THORENS TD 150AB Mk. II with 
TX11 dust cover, SHURE M55E 
Cartridge, LEAK Stereo 70 
Amplifier in Teak case. 2 Wharfe- 
dale Dovedaie 3 Speakers 224-50 175 00 



THORENS TD 125AB Electronic 
Turntable complete with cover. 
SHURE V1 5-11 Cartridge, GOOD- 
MANS Maxamp, GOODMANS 
Stereomax AM/FM Tuner. 2 
GOODMANS Maglster Speaker! 419-65 310 00 




All in-stock items delivered by 



WITHIN 72 HOURS 

(Add £1.50 only for Securicor delivery) 
ALL GOODS FULLY INSURED AGAINST 
LOSS OR DAMAGE WHILST IN TRANSIT 



1079 



DISCOTHEQUE EQUIPMENT 
PACKAGE OFFERS 



F.A.I. PHASE GO MK.II AMPLIFIER 
PR. R.S.C. L12/25 25W L/S in cabinets 
Terms: Deposit £8 and B monthly- 
pay ments of £5 (Total £64) 
F.A.L. PHASE 60 MK.II AMPLIFIER 
PR. FANE POP 60 1/ SPEAKERS 
Terms: Deposit £10.50 ami 9 monthly 
payments of £5 (Total £55.50] 
F.AX. PHASE 100 AMPLIFIER 
PR. L125 SOW L/S in cabinets 
Terms: Deposit £22 and 9 monthly 
payments ol £11 (Total £121) 
F.A.L. PHASE 100 AMPLIFIER 
4 FAKE POP 50 L/SPEAKERS 
Terrns: Deposit £14 and 9 monthly 
- ;if £10 (Total £104> 



PACKAGE 
PRICE 

£48 carr. £1 

PACKAGE 
PRICE 

£49.50 3f 

PACKAGE 
PRICE 

£H0^n 

PACKAGE 
PRICE 

carr. 



£94 



ELM 



AUDIOTRINE HI-FI SPEAKER SYSTEMS 

Consisting of matched 12tn. 11,000 line 15 Watt 16 ohm 
hitrb quality speaker. crossover unit and tweeter. Smooth 
raiDonw and extended lro<juencj tuu ^— ^> 
■Mow mrpilllncty realistic reproduction. tj,/J> 
OR SENIOR 15 WATT INC. HP12EJ ,, ,- c _ r . 30n 
15,000 LIKE SPEAKER carr. 35p tO.13 v " rr ' «W 




AUDIOTRINE HIGH FIDELITY LOUDSPEAKERS 

Heavy construction. Latest high efficiency ceramic 
magnets. Treated Cone surround, "I)"* indicates Tweeter 
Cone proviilin;; extctuled frequency range up to 15,000 
c.p.s. Impedance 3 or 8-lo ohms. Please state choice. 
Exceptional performance at low seat. 
HFS01D S" 8W £2.71 HF12GD 13' 16W £4.49 
HF102D 10" 10W £3.40 HF12B 12" 16W £6.26 
HF120 12" 15W £3.89 HF126D 12' 16W £5.76 




FANE 807 HIGH FIDELITY LOUDSPEAKER 

A lull range Sin. 10 watt unit 'or excellent strand Quality, in 
suitable enclosure. Cast chassis Boll P.T.Q. cone surround and lonrr 
throw voice coil to achieve very low fundamental resonance of 
30 c.p.a. Tweeter cone Is titled to extend hifb note response. 
Frequency range 26-15 KHz. Impedance 3 or 8-15 Q. X"l CA 
Qauis 10.000. Remarkable value. fc -»* JVF 




HI-FI SPEAKER ENCLOSURES 

Modern design. Teak veneer finish. Acoustically lined. 

All sizes approx. Carr. 25p. per enclosure 

IBS Stee 10 I 11 x Bin. Pressurised. Gives £_A TC 

pleading result* with any Sin. Hi-Fi *speaker. *»•!• * J 

SE8 For optimum performance with any Sin. XC TC 

HI-FI 'speaker. Size 22 x 15 x Bin. Ported K.9.1^ 

EE10 For outstanding results SE12 For exclnt prfmnce with 12Ln. 

with lOln. Hi-Fi 'spier ,_ „, Hi-Fi speaker and Tweeter. 

Slie 24il5ilMn. P'tet. »■" Size 2S x 16 x lOltn. 




£6.99 



RECORD PLAYING 
UNITS 



RPIC 



Money saving units. Mounted 
on Plinth. Supplied with trans- 
parent plastic cover. Ready to 
plug Into Amp. or Tape recorder. 

Garrard SO 00 4 -speed 
Auto-change Unit with 
Sonotone STA^HC Ceramic Stereo 
Cartridge. £ J 945 ^ m 

"""^Garrard SP*25 Mk HI 
fitted Goldring CSS0 high com- 
pliance ceramic Stereo/Mono cart- 
ridge with diamond 
stylus. £26.09 Carr 50 P 

RPf A Garrard 5200 Auto Unit 
nrvu flUclt stel . eo cartridge 
Plinth & Cover aa RF2C 



£15 



O titer types available with Mag- 
netic cartridges and with alternative 
design plinths. 



R.S.C. PLINTHS (or 

Superior Solid Natural Record 
Wood Conjiituition Playing 




.„ TRAHSP. 
PLASTIC COVER 



LEADING MAKES HI-FI EQUIP- 
MENT AT CLEARANCE PRICES 
Available at branches only 




R.S.C. TA6 6 Watt HI-FI 
SOLID STATE AMPLIFIER 



200-250v. A0 mains operated. Frequency Re- 
sponse 30-20,000 c.p.a, — 2dB. Harmonic Distor- 
tion 0.3% at 1,000 c.p.a. Separate Bass and 
Treble "Itrf ami 'cut' controls. 3 input sockets (or Mike, Gram, Radio or 
Tape. Input selector switch. Output for 3-15 ohm spkrs. Max, sensitivity 
5m V. Output rating I.H.F.M. Fully enclosed enamelled case, 9j x 21 x 
Sfln. Attractive brushed silver finish facia plate 10J x 3j-tn. and matching 
knobs. Complete kit of parts with full wiring XT CQ CaJT iBX) 

diagrams and Instructions. *.#.rfv - v 

OB FACTO BY BUILT WITH 12 MOUTHS' QUARAHTBE £3.45 




1 ll-Fl CUT1I1 LTP. J 



R.S.C. COLUMN SPEAKERS 

IDEAL FOR VOCALISTS AND PUBLIC ADDRESS 

All types 15 Ohms covered in Rexine Vynair 
TYPE C4100 IS ALSO SUITABLE FOR BASS GUITAR OR ELECTRONIC ORGAN 

TYPE C48S 25-30 WATTS 

Fitted four 8* high llux 8 watt speakers. 

Overall slie approx 43 X 10 x 6 in, Carr 50p 

Terms; Dep £3 and 9 monthly f\f TC 

payments £2 (Total £81) *'* ,/3 

TYPE C4I0O 100 WATTS Jnc. lourl 

live rating. Extra heavy construction. Slie approx 58x 18x 10" Acouslk-all 

filled and pressurised. Terms: Dep. £7-50 and 9 mthly. pyta. £5- jo (Total £56-55). I'J> 



TYPE C4I2S 50 WATTS 

Fitted lour 12' 11,000 line 16 watt 
speakers : Overall size approx 56 x 14 x 9 in. 
Carr 75p 
Terms: Dep. £4 and 9 monthly fffl CA 
payments £3 (Total *S1) aVAf.^W 

30 watt speakers for conserva- £CH Crt 
, £1 



30 WATT HI-FI AMPLIFIER ffi^Mg&gf. 

lint input, 2 vol. control Hi-Fi unit with Beparate Bass and Treble 
controls. Current valves. Peak output rating. Strong Rexlne covered cabinet 
with bandies. Attractive black/gold P.V.C. lacla. Neoa indicator. For 200- 
250v. A.C. maim. For 8 or 15 ohm speakers. Send S.A.E. lor leaflet. 
Terms : D eposi 1 18.70 and 9 moa thly f I Q O C 

payments nf £2,10 (Total £82.80) fcl ' • ' " 



Carr. 85p 




HIGH QUALITY LOUDSPEAKER UNITS 




11 n*x Tnnun cab hsm 

L18 18' x 8* 10 Watt LIB 12' 

10,000 lines 3 or IB 25 WATT 

ohms. State impedance 10,000 lines 

required. 15 ohms. 

£5.25 set £9.50 



Ll»,M H WATT 
Two tone Rexine and 
vynair finish. Fitted 
pair ol 12" 00 watt 
high flux speakers for 
conservative rating. 
Impedance 8-15 ohms. 
Carr. 75p £29,40 



R.S.C BASS REGENT 50 WATT AMPLIFIER 

A powerful high duality all-purpose unit for lead, rhythm, bass 
guitar, vocalists, eram, radio, tape. Peak Output ratine. +rt\ 

Loudspeaker unit optional horizontal or vertical mounting. £uU 

* Two extra heavy duty 12ln. Loudspeakers, 

~k Four Jack inputs and two Volume Controls for Carr. £1.50 

simultaneous use of up to four pick-ups or "mikes". 

Bass and Treble controls. Send S.A.E. for leaflet. ,.,„„-* 

Credit Terms Deposit £16 and 9 monthly payments of £5.75 (Total £67.75) 




FAL PHASE 50 Mkll AMPLIFIER SOW 

Solid state 4 Separ- 
ately controlled inputs. 
Plus master vol. con- 
trol. I nd. Bass and 
Treble Control**. Pro- 
tective circuit to guard 
against damage from 
accidental shorts. Output lor Speaker/s .3-30 
ohm*. Slie 17"X7*x7r- 2O0-'250v, A.C. mains. 
I.H.F.M. Output rating, fW Cfl Carr.lj'ree 




Send S.A.E. ior l.'iilli-t-i 



FAL PHASE 100 AMPLIFIER I00W 

Solid State. 4 Separa- 
tely controlled inputs 
Plus master volume 
Control. Ind. Bass 
and Treble Controls. 
Output tor speaker/B 
S-30 ohms. Protective circuit to guard against 
damage ironi accidental shorts I.H.F.M. Out- 

»"'"•"• £61.95 o,.»„ 




FANE ULTRA HIGH POWER LOUDSPEAKERS 



All power ratings are R.M.S. continuous. 
High flux ceramic magnets. Heave east 

| 'POP' 100 



Jf 1 8" 100 Watt 

14,000 gauss 
8/1511 



£22.05 



Dep: £6 and 8 monthly 
pymnts tZ (Total £24). 



'POP* 60 

1 5" 60 Watt 

1 4,000 gauss 
8/lStl 

£12.90 

Dep. £3.30 r s-.-l 9 
ntontWy pymnts. 
£1.30 (Total £16). 



FOR BASS GTJITAll, ELECT. OEGAN, :-;TC. 



years* guarantee, 
chassis. All carr. tree. 

«P0P» 50 

12" 50 Watt 

13,000 gauss 

150 £10.50 

Dep £2 and 9 
montbly pay- 
luenu £1.15 
(Total £12.35) 
Fair suitable 
all purpoaea 



FANE 
LOUDSPEAKERS 

♦POP' 25/2 
I2in. 2S WATT 

Dual Cone 15 ft (lor uses 
other than Bass Guitar 
or Electronic Organ). 

£6.75 tree' 

or Dep. £1 and 9 mthly 
payments 7Sp 
(Total £7.75), 



R.S.C. BATTERY MAINS 
CONVERSION UNITS 

I -f"! TITS BM1 

■L^BStsst. An all-dry bat- 
: tery eliminator. 
^nBI Si7.e fij i *i i 

^■^^^ 2in, approi. 
Completely replaces batteries sop- 
plyiug 1 St. and 90v. where A.C. 
mains 2OO/£50v. 50c,s Is available. 
Complete kit with diagram £3 
or assembled ready lor use £3.50 



R.S.C. All HI-FI 12-14 WATT AMPLIFIER 

PUSH-PULL OUTPUT. Two Input sockets with sep. 
voL controls lor mixing. High rensitivity. 5 valves. Bass 
and treble controls. Response ± 3dB 30-20.000 c/s. 
Hum level — 00JB. Sensitivity 40 millivolts. For 
Crystal or Ceramic PUs. Hlgb Impedance "mikes". 
For Musical Instruments etc. 
Rt.irAC mains, For 3 4 16 ohm spkrs. Complete kit. Full £IQ CQ 
Instructions and point-to-point wiring diagrams. Carr. 60p *• * V*tww 
BAE for leaflet. Twin handled metal cover £1.75 

Factory built £14.75 or Dep. £3 and 9 mthly pymnts of £1.80 (Total £17.40.) 



R.S.C AI0 30 WATT ULTRA LIKEAR 

mCl AUDI I El CD Hiijhlv sensitive. Push-Full high 
-rl HnrLiriCIt output, Hum level— TOdB, Kesponse 
± 3dB 30-20,000 o/g. jUI high grade components. Valves EF89, 
EF86. ECC83, 807, 807, (JZ34. Separate Bass and Treble Controls, 
Senslth'lty 36 millivolts. For High Impedance microphones. 
For Clttta. Schools, Theatres. Dance Halls Outdoor Functions, 
etc. For Electronic Organ, Guitar. String Baas, etc. Oram, Badio 
ith vol. controls permit such as "mike" and Fiek-up etc. to be used 
01) c/s A.C mains. For 3 and 15 ohm speakers. Com- £ I 5 75 
plete Kit of parts with wiring diagram and Instructions. Twin-handled perforated cover ** * * 
£1.75 Or factory bulit with EL34 output valves and 12 months' guarantee for £19,76 Carr. 6ap 
TEEMS : Deposit £4 and 9 mr;nt).lv Btmrotj of £2-10 ; Total £22-908. Scivl s.A.E. icr leaflet. 




or Tape. Two separate input 
lor mixing purposes, 200-2B0 



RSC TRANSFORMERS, L.F. CHOKES & RECTIFIERS 






FULLX OUABANTEED, Impregnated and Interleaved where necessary 
Primaries 200-250V, SOc's. Screened 
MIDGET CLAMPED TYPE 2* x 2f k 2iln, 

2o0v,, 60mA, 6.3v, 2a 

*>aO-n-2S0v., 60mA 6.3v 2a "_»♦_ 

FtlLLY SHEOUDED UPEIGHT MOUKTIITCI 
B60-0-2B0V. 60mA, i>.3v. 2a., 0-Ci-6.3v. 2a, J1.B5 
25O-0-25OV. 100mA, 6,8v. 4a., 0-5-S.3v. 3a. £1.99 
30O-0-3OOV. 100mA, 6.3v. 4a., 0-3-6.3V. 3a. £1.99 
3OO-O-3O0v, 130mA. fl.3v. 4a„ e.l... e.3v. la. 

For Mtlllard 610 Amplifier ........ 158-40 

350-0-3MV. 100mA, fl.3v. 4a., 0.0-fl.3v. 3a. £1.99 
35O-0-350V. 150mA. 0.3v. 4a„ 0-3-8. 3v, 3a. £2.40 
42a-0-425v. 200mA. 8.3v, 4a., e.t., 5v. 3a. £4.4fl 
425-0-423v. 200mA, 6.3v. 4a., 6.3v. 3a., 5v. 

4oO-0-4Mv." 250mA, 6.3v. 4a., e.t ., Sv . 3a. H.99 
TOP SHEOUDED DBOP-THRO' TTPE 

25O-0-2ot)v. 70niA, 6.3v. 2a,, 0-5-0.3V, 2a. £1.20 

250-0-230v. 100mA. ft.3v. 3.5a. £1.40 

2oO-0-230v. 100mA, B,3v. 2a,, 6.3v. la. . . £1.45 

330-0-3.-0V, 80mA. fl,3r. '2a., 0-5-6. 3v. 2a. £1.60 

250-0-2 30v. 100mA, 0.3v, 4a„ 0-ft-6.3v, 3a. £1.09 

300-0-SOOv. 100mA, 6.3v. 4a.. fl-G-6.3v. 3a. £1.89 
3OO-0-300v. 130mA, 6.3v. 4a., 0-.1-0.3v. la. 

SulUble for Mullard 510 Amplifier £2.35 

350-0-350V. 100mA, 6.3v. 4a., 0-5-6 ,3 v. 3a. £1,99 

350-0-350V. 150mA, fi.Sv. 4»„ 0-5-6.3v. 3a. t£M 



FILAMENT or TRAHSISTOE POWEE PACK 
Types 6.3v. Las. 45p; 6.3v. 2a. 49p; 0.3 v. 3a. 99p; 
6.3v. 6a. £1.16; l'iv. la, 60p; 19 v. 3a. or 24v. 
l.Ba £1.80 ;0.»- 18v. lis. 99p; 0-12-2fi-42v. 2a. £1.80 
CHARGER TRANSFORMERS 0-B-10v. IJa. 96p; 
2la. 99p; iia. £1.10: 5a. £1.30; 6a. £1.49; Ms. £1.85 
AUTO (Step DP step DDVHI TRAS8FORMER8 
0-110/t20v. 2OO-230-25OV., BO-80 watts 99p; 
ISO watt*. £1.70 250 watts £2.4B; 500 watts £5.25. 
OUTPUT TRANSFORMERS „ M 

SUndard Fentodc .'.,000 Q or 7,000 ft to 8 ft 45p 
Push-Poll 8 watts EL84 to 3 or 15 ft . - 75p 
Fosh-Pull 10 watts 6V6, ECL88 to 3, a, 8 or 

15 ft «.|5 

Fash-Full EL84 to 3 or 15 CI 10-12 watts . . £1.20 
Push-Pui! Ultra Linear for Mullard 510, etc. £1.99 
Push -Puli 15-18 watts, sect tonally wound 

614, KT66, etc., lor 3 or 15 ft £1.80 

Fush-PuU 20 watt high quality sectfonally 

wound EL34, rtLfi, KT6fl etc. to 3 or 15 ft £2.99 
SM00TE1MG CHOKES 150mA, 7-10H. 250 ft 
6Sp; 100mA, 1011. 200 Q 6Sp; 80mA, 10H, 
350 ft 46p; 60mA, 10H. 400 ft S6p. 



SELENIUM RECTIFIERS F. W. (Bridged) 
All 6/12v. D.C. output. Mai. A.C. input 18v. 
la. 86p. 2a. 36b. 3a, 50p. 4a. 86p. 6a. BOp. 



1080 



Introducing R.S.C. Mklll SUPER 30 HI-FI STEREO AMPLIFIER 



A COMPLETELY NEW DESIGN 
FURTHER IMPROVED IN BOTH 
APPEARANCE and PERFORM- 
ANCE. REPRESENTING VALUE 
FAR HIGHER THAN THEfJftC 
PRICES SUGGEST. Only**** 
high grade components by leading 
manufacturers. Complete kit of parts. 

Or FACTORY BUILT with 12 £•>■» TF 
month* guarantee fc<JiJ. * rf 

Or FACTORY BUILT in cabinet as illustrated £JA « 

PR1NTEO CIRCUITRY. TWENTY SILICON TRANSISTORS. 

FOUR DIODES, FOUR RECTIFIERS. 

TECHNICAL DETAILS (Applying to each channel where appropriate) 
CONTROLS: PUSH-BUTTON SELECTOR (1) Disc (2) Radio (3) Tape (4) Mono L 
(5) Mono R (8) SPEAKER DIS. (7) Main* on/off 




* SATIN SILVER METAL FACIA with black letter- 
ing. Black edged knobs with bright silver centres. 

* PUSH-BUTTON SELECTOR SWITCHING 

* NEON INDICATOR 

* JACK SOCKET FOR HEADPHONE 
CONNECTION 

* CABINETED MODEL VENEERED IN SATIN 
TEAK. SUITABLE FOR ANY MODERN PICK- 
UP CARTRIDGE or MAGNETIC, REGARDLESS 
OF PRICE. WE RECOMMEND USE WITH THE 
BEST ANCILLARY EQUIPMENT THAT CAN 
BE AFFORDED. 



OUTPUT: IS watt* R.M.S. (Continuous) into 8 ohms HUM and NOISE-TSdB 
Min. Vol. 10 watt* R.M.S. {Continuous) into IB ohms-65dB Full Vol. 
FREQUENCY RESPONSE :-3dB 7Ki to 70KH* HARMONIC DISTORTION 
TREBLE CONTROL: +18dB to-12dB at 14KHi 0-1% at 1000 Hz ID W 

BASS CONTROL: -H7dB to -16dB at 40Hi CROSS TALK -S8dB 

SENSITIVITIES: Disc Mag. 2 SmV. Ceramic 35mV. Radio 120mV. Tape 120mV. 
REAR PANEL SOCKETS ARE FOR 3 PAIRS OF INPUTS (1) P.U. (2) Radio. 
(3) Tape Amp. Plus pair for tape recorder ilgnal takeoff and 2 pairs for loudspeaker 



Ban, Treble, and Riiaqci. Plus Ceramic/Mas P.U. Switch. connection*. 

;Mtl.irHilBli]fl.i'l.iiflji,JiTri:fTH <i]JJtk 

Four fully wired units ready to 'plug in." Matching as recommended (or optimum performance. Send i( TA12 AMPLIFIER 



SUPER 30 AMPLIFIER (15 + 15 S. A. E for coloured brochure showing other money -sa vine oHers, 
watt) in veneered housing 
GARRARD SP25 MKHI Turntable on 
Plinth with cover 

GOLDRING CS90 Ceramic P.U. Cart- 
ridge with diamond stylus 
PR, OF STANWAY II jp7Q Oft 
Speaker Units *I«'WO 
Special Total Price c*rr. £1.80 



* Super 30 Amplifier (15 + 15 watt) 

in veneered housing 
if Goldring GL69 Transcription Turntable 

on Plinth as illustrated 
if Goldring Magnetic P.U. Cartridge. 




Package prices apply providing 
all individual units are purchased 
from any branch within 3 months. 

See leaflet. 





ATTRACTIVE TEAS or AFEOBMOBIA 
7EJTEEEED CABIzTETS tad PLUTHJ 



if Pair of Stanway II fftJ* TC 

spec^TltTplice 2^„ TERMS AVAILABLE ON All PACKAGE OFFERS 



AUDIOTRINE A55 HIGH QUALITY STEREO SYSTEM 



5 + 5 WATT OUTPUT 

QARRARD SIM Changer 
with low ma»* pick-up arm 
and Stereo Cartridge. CON- 
TROLS: TREBLE, BASS, 
VOLUME, STEREO, BAL- 
ANCE. 

Operation on 200 - 250v, 
A.C. mains. 
Output rating. I.H.F.M 



PAIR OF 
LOUDSPEAKER UNITS 

incorporating high flux 

8 x S ins. speaker. 

Size approx. 13 x 7j x 8f ins. 

Price complete f AO 
ONLY *>*tfc 

Can-. £1.35 
Luxurious Teak Veneer Finished Cabinets. Transparent Terras: Deposit £5*50 and 9 
plastic (tinted) cover Included for main unit. Silver monthly payments £4,50 
finished fa da plate and mat eh log control knobs. (Total £46 ) 

A REALLY SURPRISING STANDARD OF QUALITY IS OBTAINABLE FROM THIS COMPACT LOW PRICED SYSTEM 




6.5+6.5 watt in veneered housing 
if GARRARD SP25 MK III Player 

unit on Plinth 
if GOLDRINGCS90 Ceramic P.U. 

Cartridge with diamond stylus 
• PAIR OF DORCHESTER 

Loudspeaker Units 

Special OCO C ** T - 
Total Price AvO £125 
Or Deposit £7.15 and 9 monthly 
payments £6.35 (Total £64.30). 
Trans. Plastic Cover £3.15 extra. 
Package a* above bat with Garrard 3000 Ante— 
dtinger and Sonoton* STA Ceramic Cart- 
ridge In lieu ol HFSJS /CI 7C Cair. 

»nd cseo »V3 1 . # a £1>26 

Or Deposit £6 and 9 monthly 
payments £5.70 (Total £57.60) 
Trans. Plastic cover £3.15 extra. 



LOW DEPOSIT 
CREDIT TERMS 



AVAILABLE ON PURCHASES OVER 
£8 (KITS OF PARTS EXCEPTED) 

INTEREST CHARGES 
REFUNDED 

OK CREDIT SALES SETTLED IK 3 MONTHS 



RSC G66 6+6 WATT high quality STEREO AMPLIFIER 



Individual Ganged controls: Bass, Treble, Volume and Balance. Printed 

circuit construction employing 10 Transistors plus Diodes. Output 

rating I.H.F.M. Suitable for Crystal Pick-ups, etc., and for loudspeaker 

output impedances of 3 to 15 ohms. For standard 200 — 250 v A.C. 

mains operation. Attractive silver finished 

metal facia plate and matching control 

knobs. 

Complete KIT of PARTS INCLUDING 

FULLY WIRED PRINTED CIRCUIT 

and comprehensive wiring £Q OO 

diagram and instructions ***•" 

Or FACTORY BUILT IN TEAK VENEERED No leaflet supplied 

CABINET as illus. £12.50 carr 40p, for this unit, 

or dep £2 and 9 mthly pymnts. £1.45 (Total £15.05). 




'YORK* HIGH-FIDELITY 3 SPEAKER SYSTEM 

£22 



it Moderate size only £5 x 14 x lOin. COMPLETE 

■k Response 30-20,000 c.p.s. Impedance 15 ohms KIT 
•k Performance comparable with unit* costing Carr. Bflp 

considerably more. Consists of (1) 12in, 15 watt Baas unit with cast chassis. 
Boll rubber cone surround for ultra low resonance, and ceramic magnet. 
(2) 3-way quarter section series cross-over system. (3) 8 x Bin. high flu* 
middle range speaker, (4) High efficiency tweeter. (6) Appropriate 
quantity acoustic damping materia] (01 Handsome Teak veneered cabinet. (7) Circuit 
and toll Instructions, Terms: Dep. £4-80 and 9 mtflly. pyrats. £2 £5 (Total £24 75) 

DEMONSTRATIONS AT ALL BRANCHES 




HIGH FIDELITY LOUDSPEAKER UNITS cabinets latest 

style Satin Teak or Afrormosia teneer. Acoustically lined or filled 
acoustic damping. Ported where appropriate. Credit terms available. 
DORCHESTER Size 16 X II x 9in. appr. Range 45-15,000 c.p.s. 
Rating 8-10 watts. Fitted High flux 13 X Sin. £Q 45 
Dual Cone speaker. Imp. 3 or 15 Ohms. w.-w carr.40p. 

STANWAY II Size 20 x 104 X 9Hnu approx. Rating 10 watts. Inc. 
13 x Sin. speaker with highly flexible cone surround, long throw voice 
coil and 11,000 line magnet. High flux tweeter. Handsome Scandinavian 
design cabinet. Range 35-20,000 c.p.s. Imp. 15 ohms. Gives f 17 oc 

omru-it}i reolifitte Bfiimfl niitmit See above for illustration *■' ''"' 




smooth realistic sound output. 



R.S.C. TAI2 HKIII 6-5 + 65 WATT STEREO AMPLIFIER 

FULLY TRABTSDJTOBISED, BOLID STATE COHSTBUCTIOH 
HIGH FIDELITY OOTFOT OP 8.5 WATTS PEE CHANNEL 
Designed for optimum performance with any crystal 
or ceramic Oram. P.U. cartridge, Sadie toner. Tape 
recorder etc, if 3 separate switched Input 
sockets on each channel + Separate Bans and Treble 
controls -jc Blide Switch for mono use -Jr Speaker Out- 
put 3-18 ohms ir For 300-250 v. A.C. mains jr Fre- 
quency Response 20-20,000 c.p.s,. — 2dB it Harmonic 
Distortion 0.3% at 1,000 cp.s. Hum and Noise - 70dB in Sensitivities (I> 50m V (2) 
400mV (3) lOOmV. Outpnt rating LH.FJ t, jr Handsome finish Facia plate & Knobs. 
COMPLETE KIT OF PABTfl WITH PT/LL WTRIHS DIAGRAMS & IHSTBUCTIOHB. 
Factory built with 12 monfhi guarantee £19.50 or Deposit £8 and r | r rn Carr. 
9 mtiiiy pvmts £8.08 (Total ££1.48). Or In Teak veneer housing *■ ' 3 ' w 40p, 
£23 Dep. £3 & 9 mthly payments £3.58 (Total ££S,9B). Send S.A.E. tor leaflet 




PARTRIDGE "JOYSTICK" SHORT WAVE AERIALS AND TUNERS AT ALL BRANCHES (S.A.E. for full list) 



BRADFORD I0 North Parade. (Half-day Wed.) Tel. 25349 
BLACKPOOL (A « ont> °' & Cl Electronics, 227 Church 

BIRMINGHAM 30/31 Gt, Western Arcade (Hair-day 
HI KFI I HUH AH Wed ., 021-236-1279 

DERBY 26 ° 5maItor ' M - Tne Spoc (Half-day Wed.) Tel. 

DARLINGTON IS Priestgate (Half-day Wed.) Tel. 68043 
EDINBURGH 133 Leith St. (Half-day Wed.) Tel, Waverley 

GLASGOW 326 Argytc St. (Half-day Tues.) Tel. CITy 4158 
HULL 91 Paragon Street (Hatf-day Thursday) Tel. 20505 



RSC 



HI-FI CENTRES LTD. 

MAIL ORDERS TO: Audio Home, 

Henconner Lane, Leeds 13. 
Terms C.W.O. or C.O.D. No C.O.D. 
under £1. Postage 25p extra under £2. 
30p extra over £2 or as Quoted. Trade 
supplied. S.A.E. please with enquiries 
Branches open all day Sats, 
MAIL ORDERS MUST NOT 
BE SENT TO SHOPS 



32 High Street (Half-day Tours.) Tel. 56420 LEICESTER 
5-7 County(Meeea) Arcade, Briggate (Half-day Wed.) I EC|)C 

Tel. 28252 I-""* 
73 Date St. (Half-day Wed.) Tel, CENtral LIVERPOOL 
238 Edgware Road. W2 (Half-day Thurs.) Tel. LONDON 

60A Oldham Street (Half-day Wed.) MArJCrlF^TFR 

Tel. CENtral 2778 OWntnCJICn 

106 Newport M. (Ha.f-day WedJ MIDDLESBROUGH 

41 Blaekett Screes ; (Opp_Fenwieks_ NEWCASTLE UPON 



TYNE 

13 Exchange Street (Castle Market Bides.) CUCCCipi Q 

ay) Tel. 20716 JnCrriELW 



Store) (Half-day Wed.) Tel. 21469 
e Street (Castle I ' 
(Half-day Thursd, 



1081 





MARCH ISSUE 




FURTHER MODIFICA- 
TIONS TO THE 'TRIO 1 

9R-59DE 

In Part 1 of this two-part series, 
the author describes a series of 
comparatively simple modifica- 
cations which collectively great- 
ly improve the performance and 
stability of this popular com- 
munications receiver. 

Part 2, to be published in the 
April issue, deals with the more 
complex modifications. These 
consist of an EF183 r.f. stage, an 
added i.f. stage with double- 
tuned i.f. transformers, tape 
recorder output and full r.f, 
alignment details, etc. etc. 



MTT 



hi 



Also 

TIMER WITHOUT 
ELECTROLYTICS 

To obtain sufficiently long 
timing periods, the current 
trend in electronic timers is to 
employ an electrolytic com- 
ponent as the timing capacitor. 
This article describes a timing 
circuit which, by taking advan- 
tage of a pulsed transistor, 
enables a paper or plastic foil 
capacitor to be used instead. 



PLUS 
MANY OTHER PROJECTS 

ON SALE NOW 3/6 

Copies may also be obtained 
direct from the Publishers 

4/- including postage. 
Published by: 

Data Publications Ltd. 
57 Nlaida Vale, London, W.9 



RADIO CONSTRUCTOR 



1082 



LOOK AT THESE PRICES 

CARTRIDGES 

Acos GF67-2. OP91-35C II -18*; Acqs GF03-1 
£1-331: Aeos GP94-1 11 82t; Sonotone 9TA1IC 
11071; All above in makers cartons; BSR X4H 
II. M. 

FS £400 STEREO AMPLIFIER 
5 watts per channel; Id attractive Cabinet. P.I". 
Radio & Tape inputs Tape output & Speaker outputs 
Dim, 12 T - x Sf x 3J\ Our Pita £18-97*. 

Picas A SOCKETS 

Phono plugs, assorted colours dp; 45p per doz; 
Coaxial plugs, aluminium 7[p; Coaxial couplers 7(p; 
2 pin DIN plage lBp: 3 pis DIN plugs 15j>; 5 pin 
DIN pings 17p : 2 pin, 3 pin & S pin DIN sockets 7t p ; 
Wander plugs 2fp; sockets SJp; Banana plugs 6} p. 
Sockets Gp ; 3-5mm J/ Plugs 75 p and ISip ; Standard 
J iPlaga with solder terminals lOp ; Chrome 15p : 
Side Entry J/Plugs black and chrome 24p ; Insulated 
j/sockets — o/cct 16p, c/cct 17p. 

ELECTROLYTIC CAPACITORS 
4uF IGOv 4p ; SuF BOOv ISp ; 8uF 12 v 4p ; SuF + 
8oF ISOv 21p : lOuF IBOv 4p : 12uF 25v 4p ; lfloF 
400v 14p ; 16uF 4- lSoF 450v 23 r p ; 30nF lOv 4p ; 
60uF lOv 4p ; lOOuF 9v 4p ; lOOuF 12v 4p ; 150uF 
12v 4p : 320uF Ov Sp ; lBOOuF 30v 19p ; lOuF 16v 
7}p ; oOOOnF 25v 50p | IO.OOOuF 25v 7Sp ; 20.000uF 

HrM 

MICROPHONES 

Ai-ns Mic 4S £1.121; Am« Mic 60 OBjp; Planet 

CM70 81-50; Hand Mike 75c. 

VALVES 

PTSt S8p; PCLH 3Bp: EF183 45p: EFI84 4Gp. 

PLEASE NOTE CHANGE OF ADDRESS 

GEORGE FRANCIS (Dept PW), 

12-14, Middle Gate, Newark, Notts. 
Telephone: Newark 47S*. 



Vary the strength 
of your lighting with a 

m 



i 



mi 




4 



r > 



The DIMMASWITCH is an attractive and 
efficient dimmer unit which fits in place of 
the normal light switch and is connected 
up in exactly the same way. The ivory 
mounting plate of the DIMMASWITCH 
matches modern electric fittings. The 
bright chrome control knob activates an 
on-off switch and controls 40-600 watts of 
ail lights except fluorescents at mains 
voltages from 200-250 V. 50 Hz. The DIM- 
MASWITCH has built-in radio interference 
suppression. Price; £320 plus 8p post and 
packing. Kit Form; £2-70 plus 8p post and 
packing. Please send C.W.O. to:— 

DEXTER & COMPANY 

1 ULVER HOUSE, 19, KING STREET, 

CHESTER CH1 2AH Tel: 0244-25883, 

As supplied to H.M. Government Departments, 
Hospitals, Local Authorities, etc. 



BRAND NEW AR88D COMMUNICATIONS RECEIVERS. 
AG mains input 110 volts or 350 volte. Frequency in fi 
bands 535 k/es up to 32 megs, output impedance 2-5- 
600 ohms. Complete with crystal niter noise iimiter 
B.F.O. HF tone controls. Price £80 Including spare net 
of valves, headphones ana manual. 

COMPUTER BOARDS Min 30 transistors and diodes and 
rods, etc 10 boards at 50p plus 12|p p.p.; 20 boards at 
£1-12} plu* 22Jp p.o. 

BARGAIN PARCELS 141b at £1 45 plus 3JJ p p.p.: 281b at 
£2-75 plus 521 p PP- : 561b at £4 SO plus £1 26 p.p. Contain 
pots, Rw, Valves, Diodes. Tagboards, Chassis, Valve- 
holders, etc. Good value save £££s. Lucky Dip Service. 

FURZHILL BEAT FREQUENCY OSCILLATOR 0-10 

kc/s, 110/250 volt. Good condition complete with spares. 

£ 5 50 plus £1-20 p.p. 

VHF Receiver , Type 715, less crystal 60-100 Jtc/s can be 
operated on 2 or 4 meters or made tunable 12 volt input, 
not tested ; complete with valves and speaker. 

£3 plus £1 p.p. 

VHF AERIAL TUHIHG DUITS consisting of the lollowing : 
l-lj" 500 mloro/ampmeter. 1 small 2-gang 75 PF 
capacitor, 1 various large wattage resistors for dummy 
load. Pair gears B.N.C. type sockets. Will tune 10 mtrs 
with 25/30 watts K.F. input, 8 lie only 5f X 4 J* X 5* 
Sealed. Price £1-371 p.p. 2Sp 

CRYSTALS A3 HEW: He 6u. 5.345; 5.030; 5,005; 4,045; 
4,875: 4,340; 4,795; 4.580: 4,680: 4,820: 4,510; 2,300: 
2,205 Kc/is and 10 x J465 Kc/s. Mp each plus 8p. p.p. 

SCOOP PURCHASE OF BRAKD HEW CARB0H RESIS- 
TORS. 10% tolerance J & , watt. Preferred values hi 
packets ol 10, Our price 50p per 100, 50p per 300, £1-85 per 
300, 500 at £212!. Our selection, p.p. Sp per 100 and 2)p 
per extra 100. 

TRIMMER BARGAINS. These are 10 PF sub .min. atr- 
~ paced trimmers on board with min. wire ended XtaL 
Brand mw. No details; Content* 12 trimmers, some 
ceramic caps. Xtal frequency 3RD overtone 240 me/s- 
250 Mc/n, 256 Mc/s. No choice. 

Trimmers without Xtal — 60p per doz, plus 17fp p.p. 

Trimmers with Xtal — 75p per doz. plus 171p p.p. 
Also 20 PF min. brand new air spaced. 

SOp per doz. plus I7}p p.p. 

HRO MXS IH EEW COEDITIOH with 5 general coverage 
L-oil units including spare set of valves less power supplv. 
Tested M p.p. £1-50. 

AST HEIGHT AERIAL TUBULAR 8ECTI0KS I' dta 
x 3 ft. long. Brass screw in type, copper coated and 
painted. New 80p each, p.p. 5p. Minimum order 6. 

SIGNAL GENERATORS OSCILLATOR HO. 8. Size 12m. i 
8 1 in. x Oln. Ideal for VHF work. 20-80 Mc/s. Functions 
are AM/CW, Deviation up to 40 Ko/s RF meter. Measur- 
ing levels: RF output 1 microvolt to 100 micro volts set. 
Mod -set carrier controls. Good condition with accessories: 
230V AC 12V DC. £80 plus 75p p.p. 

R809 RECEIVER AM/CW/FM 1-20 m/ca, four band™ 
vernier tuning, 12 volt D.C. Input tested and working. 
Price £16, p.p. £1. 

AERIALS HEW C0HDITI0H. Whip type 4ft. B6», lift- 
62ip, 14ft. 77lp. Used condition 4ft. 20p, 14ft. B2iP- 
All collapsible type p. and p. 4ft. 10p, rest at 17Jp. 
Bases for above 25p, p.p. 2/6. New matching unit coax 
connection for above 80p, p.p. 5p. 

Huge release of valves for the 62 set TX/RX, in original 
rubber packing consisting of QV04/7 X 61M, ARP12 etc, 
10 valves In all at tbe bargain price as seen 

87ip pins 17Jp p.p. 

New Read phone and Mike rubber muff type. Low 
impedance. B7ip. p. 4 p. 17ip. 

Magnetic Transducers new, price S?|p post and packing 
lOp. 

R"ew Aerial Wire on boards 7/22 uncovered. Length 76fl. 
•Op, 90ft. 471B, 100ft. 55p, p.p. 12(p. 

New small fuse boxes 250 volts 15 amps. S7rP each post 
and packing 15p. 

Headphones, ex Gov. DLR No. 5 high impedance 
New 87ip 1 7 ip p.p. Used condition 82)p l"ip p.p. 

Meters moving coll ex equipment, good condition. Also 
20 amp DC, 40 amp DC, and RF Therm-Couple Meten 
0-1 amp and 0-2-5 amp, 2in. diameter. SOp post and 
packing 2Bp. 

C W.O. CARRIAGE CMAKGE8 MAINLAND ONLT 

A. H. TH ACKER, 

Radio Dept,, 
HIGH STREET, CHESLYN HAY, 

Nr. Walsall. Staffi. 






Practical Wireless Classified Advertisements 

The pre-paid rate for classified advertisements is 8ip per word (minimum 12 words), box number 7±p 
extra. Semi-displayed setting £6 per single column inch. All cheques, postal orders, etc., to be made 
payable to PRACTICAL WIRELESS and crossed "Lloyds Bank Ltd." Treasury notes should always 
be sent registered post. Advertisements, together with remittance, should be sent to the Classified Ad- 
vertisement Manager, PRACTICAL WIRELESS, IPC Magazines Ltd., Fleetway House, Farringdon 
Street, London, EC4A 4 AD for insertion in the next available issue. 



MISCELLANEOUS 



— TOP TRANSISTORS — 

Brand New and Individually Tested Trin- 
t it tors supplied unmarked, but packed 
separately for mdentification and guaranteed 
to be within their correct specification or 
money refunded. All at 9p. each or 

Any 16 transistor* for only £1. 
ACY22 BSY27 OC20I 2N3702 

BCID8 OC45 OC202 2N3703 

BCIOT OC7I ZTX3Q0 2N370S 

BFY5I OC72 2N706 2N3706 

BFYS2 OC200 2N2926 2N3708 

Money back guarantee. P. St P. Sp. 

j. M. KING (C) 

17 Buckridge, Portpool Lane, 

London, E.C.I 



12 VOLT 
FLUORESCENT LIGHTS 



1 2 ins, 8 Watt tube ample tight for caravan, 
tent, etc. Fully transistorised, low battery drain. 
Unbeatable at f T .97 I 

*>*> fcl"! postpaid 
or in kit form £0 ■ft7— 



BIG BARGAIN PARCEL 75 p 

POST PAID 

Containing multi -con tact relay, transistors, 
resistors, rectifiers, diodes, capacitors, pots, 
knobs, etc 

4 WATT GRAM AMPS. 

Volume and tone control!, mains operation. 
If] output, new and boxed £X>fj% p °5 



SALOP ELECTRONICS 

U WyU Cop 
Shrewsbury, Shropshire 



PAID 
Catlert welcome 
S.A.E. for frits 



MUSICAL MIRACLES 

WAA-WAA Pedal. Complete kit of all 

parts, robust cabinet, mechanism <te 

Instructions. Huge sales, well proven 

design. Only £2.45 complete. Or built & 

tested £4.75 post free. 

Rhythm Box. Build your own from our 

pre-bullt electronic circuit modules, e.g. 

box giving waits, foxtrot etc,, cost under 

£17. 

Organ Percussion units £14. Boss pedal 

and other fascinating effects, fun, 

tremolo etc. 

Send s.a.e. for list. D.E.W. Ltd., 

254 Ring wood ltd.. Fern down, Dorset. 



ENAMELLED COPPER WIRE 



S.W.G. 

18-22 
23-30 
31-35 
36-40 
41-44 



Per l 2 lb reel 
E0,62i 2 
£0.65 
£0.67*2 
£0.82J 2 
£0.97i 2 



Per lib reel 
£0.92*2 
£0.97» 2 
£1.02> z 
£1.32 » 2 
El.62'2 



Orders despatched by return of post. 
Please add £Q.12' 2 per item P. & P. 

Supplied by: Banner Transformers, 
Brooks St., Higher Hillgate, Stockport, 
Cheshire. 

TRADE ENQUIRIES INVITED 



MISCELLANEOUS 

(continued) 



BUILD IT in a DEWBOX quality 
cabinet. 2in x 2 J 2 in x any length. 
D.E.W, Ltd., Ringwood Road, FERN- 
DOWN, Dorset. S.A.E. for leaflet. Write 
now— Right now. 



We stock all those components and 
materials required by the home Hi-Fi 
constructor, including speaker grille 
fabrics, BAF wadding. Peerless speaker 
kits, Helme Cabinet Kits, cross-over net- 
works, inductors, etc. Special offers also 
available. Send stamps to value of lOnp 
NOW for your copy of our new fully illu- 
strated catalogue (catalogue cost refunded 
against purchases over 50np) , No callers 
please, mail-order ONLY. 



TW.H-UWCT 



D.pt PW< 



4, PRINCES SQUARE, 
HARROGATE, YQRKS. 



ELECTRONIC ORGAN 

Solid state generator, 72 or 84 note 
with vibrato, Mullard pot cores, silicon 
N.P.N. Transistors, plug-in dividers for 
easy assembly and servicing. All parts 
standard. Ideal basis for any size of 
organ, will suit most set-ups. Large 
drawings and instructions £1 post paid. 

SEON SMYTH, 
234 Dumbarton Road, 
Partick, Glasgow W,l. 

SINCLAIR PROJECT 60 OFFFEBS. Two 

Z30 amplifiers, stereo 60 pre-amp, PZ5 
power supply £18-75, or with PZ6 
power supply £20-75. Two Z50 ampli- 
fiers, stereo 60 pre-amp, PZ8 power 
supply £20-75. Transformer for PZ8 £3. 
Q16 loudspeaker £7 90, Project 60 
tuner £20-75, Other offers: S-DeCs 95p. 
T-DeCs £2 10. Modem miniature 
meters, l s 4 in. square, similar to SEW 
38p, 50 or 100 microamps £1-50. Sin- 
clair Micromanic receivers, kit £2-20, 
assembled £2-70, batteries 27p extra. 
PNP Silicon transistors 2S300 series, 
untested but at least 807c are good, 
50 for 40p, 100 for 70p. All goods are 
brand new. Money back if not satisfied. 
We regret that we are at present 
handling only mail order business. 
Postage 37p on Project 60 orders, lOp 
on others. — Swanley Electronics, 32 
Goldsel Road, Swanley, Kent. 

'DHtECTORY'; 450 paraphysical cases, 
Britain. Unusual electrical effects. £2. 
Paralaboratory, Downton, Wilts. 

LETCH WORTH, Electronic Com- 
ponents, Communication and test 
equipment servicing. Open on Satur- 
day only. W.T. Communication and 
Electrical, 14 Dixmore Yard, off Dix- 
more Avenue, Letch worth, Hertford- 
shire. (Turn in by Jet Garage in Dix- 
more Avenue.) 

DAILY UFO FLIGHT PATTERNS 

(British, American), 37 1 2 p. UFO Map, 
S. England, 37* 2 p. TV Notes on UFO 
Detection, and 2 Optical Circuits, 50p. 
Radar & Electronic Publications, "High- 
lands," Needham Market, Suffolk. 



MISCELLANEOUS 

(continued) 



ENGINEERING SERVICE for construc- 
tors. Lathe work, milling, sheet metal, 
castings, etc. S.A.E. for details. Chelms- 
ford Machine Tool Company, P.O. Box 
55, Chelmsford CM1 2AU. 

SERVICE MANUALS for Pre 1958 
H.M.V. and E.M.I. MODELS. Radio and 
Record Player Manuals 25p each. Tele- 
vision Manuals 37' 2 p each. SendC.W.O. 
stating model required. Also limited 
range qf components and spares. Send 
details of your requirements. R.D.I. 
Ltd.. Chilton Works, Garden Road, 
Richmond Surrey. 



THE NEW 

ELECTRONIC MUSIC FOR YOU 

Then how about making yourself an elee- 
tric organ? Constructional data available 
— full circuits, drawings and notes! It has 
5 octaves. 2 manuals and pedals with 21 
stops — uses 41 valves. With Its variable 
attack you can play Classics and Swing. 
Write NOW for free leaflet and further 
details to C. & S., JO Maude Street. 
Darlington, Durham. Send 2p stamp. 



WANTED 



CASH PAID for New Valves. Payment 
by return. WILLOW VALE, ELEC- 
TRONICS, 4 The Broadway, Hanwell, 
London, W.7. 01-567/5400-2971. 

WE BUY New Valves and Transistors. 
State price: A.D.A. MANUFACTURING 
CO., 116 Alfreton Road, Nottingham. 

WANTED NEW VALVES, televisions, 
radiograms, transistors, etc STAN 
WILLETTS, 37 High Street, West Brom- 
wich, Staffs. Tel.: WES 0186. 

WE BUY New Valves, Transistors and 
clean new components, large or small 
quantities, all details, quotation by 
return. WALTON'S WIRELESS 

STORES, 55 Worcester Street, Wolver- 



hampton. 



TOP PRICES PAID for NEW VALVES 

popular T.V. and Radio types. 

KENSINGTON SUPPLIES (C). 

367 Kensington Street, Bradford 8, 
Yorkshire. 



HIGHEST CASH PRICES for Tape 
Recorders, 9.30 - 5, Immediate quota- 
tions. 01-472 2185. 



WANTED NEW 
VALVES ONLY 

Must be new and boxed 
Payment by return 

WILLIAM CARVIS LTD. 
103 North Street, Leeds 7 



1083 



EDUCATIONAL 







TELEVISION AND RADIO TRAINING 

(DAY ATTENDANCE COURSES) 

This private College provides theoretical and practical training in Radio & TV Servicing. Courses 
of one years' duration, with daily attendance, are available for beginners and shorter courses for 
men with previous training in Electronics and Radio. Training courses in Radar and Radio Trans- 
mission are also available following the TV course. Write for prospectus to; — 
London Electronics College, Dept B/4, 20 Penywern Road, Earls Court, London, S.W.5 

Tel. 01-373 8721 



MEN! You can earn £50 p.w. Learn 
Computer Operating. Send for FREE 
brochure — London Computer Opera- 
tors Training Centre, C94 Oxford 
House, 9-15 Oxford Street, London, W.l. 



R.T.E.B. Certs., City & GuOds. Colour 
TV, Radio, Computers, Radio Ama- 
teurs' Cert., Practical Electronics (with 
kit). Thousands of successes. Send for 
full details of Home Study Courses and 
illustrated book— FREE. BRITISH IN- 
STITUTE OF ENGINEERING TECH- 
NOLOGY, Dept. 137K, Aldermaston 
Court, Reading RG7 4PF. 



A.M.S.E. (Elec), City & Guilds, R.T.E.B. 
Cert., Radio Amateurs' Cert., etc., on 
'Satisfaction or Refund* terms. Wide 
range of courses in Elec. Engineering, 
Design, Installation, Repairs, Refrigera- 
tion, Electronics, Radio & TV., etc. 
Send for full details and illustrated 
book — FREE. 

BRITISH INSTITUTE OF ENGINEER- 
ING TECHNOLOGY, Dept. 124K. Alder- 
maston Court, Reading RG7 4PF. 

RADIO OFFICER training courses. 
Write: Principal, Newport and Mon- 
mouthshire College of Technology, 
Newport, Mon. 



TRAIN FOR SUCCESS 
WITH ICS 



Study at home for a progressive 
post in Radio, TV and Electronics. 
Expert tuition for City & Guilds 
(Telecoms Techn's Cert, and Radio 
Amateurs') R.T.E.B., etc. Many 
non-exam courses incl, ColourTV 
Servicing. Numerical control & 
Computers. Also self-build kit 
courses — valve and transistor. 

Write for FREE prospectus and find out 

how ICS can help you in your career. 

ICS, DEPT. 541 INTERTEXT HOUSE, 

STEWARTS ROAD, LONDON. SWt 



AERIALS 



BAKER AND RAINES 
UHF AERIALS 
BBC and ITV 635 Colour: 10 ele £2.10; 14 ele 
£2.35; 18 ele £3.25; 22 ele £3.75. BBC 405 
Aerials: Dipole £1.75; X aerial £2.15; H 
aerial £2.40; 3 element £5.20; 4 element 
£6.90. ITA 405 Aerials: 5 element £1.50; 3 
element £2.70: 11 element £3.30; Double 5, 
8 and 11 arrays available on request. Com- 
bined BBC-ITA 405 Aerials: Dipole plus S 
£2.70; Dipole plus 8 £3.10; H plus 5 £4.10; 
X plus 5 £4.50. Loft special Dipole, plus 5 
£2.40. Diplexers. Triplexers. Matched 
Diplexers UHF/VHF, Poles. Lashings, Clamps, 
Couplers, etc. Coax 6p and lip. Postage paid 
inland on aerials. Please state channel re- 
quired when ordering. SAE will bring full 
lists. 



KETAL WORK 



METAL WORK: All types cabinets, 
chassis, racks, etc., to your specifica- 
tions. PHILPOTTS METAL WORKS 
LTD., Chapman Street, Loughborough. 



SITUATIONS VACANT 

MELD BENCH ENGINEER required 
for Hi-Fi firm in Wimbledon. Must 
drive. Good salary and prospects. 
Please telephone 01-540 6543. 

EAGLE INTERNATIONAL require 
Audio Engineers; excellent prospects. 
Must be fully conversant with Stereo 
Amplifiers, Tuners, Multiplex, etc. 
Contact Mr. Morrow 01-636 0961. 

Radio 
Operators 

There will be a number of vacancies in the Composite 
Signals Organisation for experienced Radio Operators 
in 1971 and subsequent years. 

Specialist training courses lasting approximately 
3 months are held at Intervals. Applications are now 
Invited for the coarse starting in September 1071. 

Salary Scales 

During training with free accommodation provided at 
the Training School : — 

Age 21 £848 per annum 

22 *90fl „ 

23 £<I43 „ 
34 £981 „ 
2S and over £1,023 „ 

On successful completion of course; — 
Age 31 £1,073 per annum 

32 Cl.140 „ 

23 £1,207 „ 

24 £1,974 „ 

25 (highest age point) £1,361 „ „ 

then by 6 annual increments to a maximum of 111,98a 
per annum, 

Excellent conditions and good prospects of promotion. 
Opportunities for service abroad. 

Applicants roust be United Kingdom residents' 
normally under 35 years of age at start of tralnlbg 
course, and most have at least 2 years operating 
experience or PMG qualifications. Preference given to 
those who also have GCB "O' level or similar quallti- 
cation. Exceptionally well qualified candidates aged 
from 36-40 may also be considered. 

Interviews will be arranged throughout 1971. 
Application forms and further particulars from: 

RECRUITMENT OFFICER < TR ° '•> 
Government Communications 
Headquarters, 
Oakley, Priors Road, 
CHELTENHAM, Glos. GL52 5A J 
Tel: Cheltenham 21491 Ext 2270 

SERVICE SHEETS 

SERVICE SHEETS. Radio, TV etc. 8,000 
models. List lOp. S.A.E. enquiries. 
TELRAY, 11 Maudland Bank, Preston. 

RADIO, TELEVISION over 3,000 
models. JOHN GILBERT TELEVISION, 
lb Shepherds Bush Rd,, London W.6. 
SHE 8441. 

SERVICE SHEETS (1925-1971) for Tele- 
visions, Radios, Transistors, Tape Re- 
corders, Record Players, etc., by return 
post, with free Fault-Finding Guide. 
Prices from 5p. Over 8,000 models 
available. Catalogue I3p. Please send 
S.A.E. with all orders/enquiries. Hamil- 
ton Radio, 54 London Road, Bexhill, 
Sussex. 



SERVICE SHEETS 

(continued) 



TRADER SERVICE SHEETS 

5/— each plus postage 

We can supply Trader Service Sheets for 
most makes and types of Radios, Tape 
Recorders and Televisions — Manuals for some. 



Cheques and open P.O.s returned if sheets not 
available. 

OAKFIELD ENTERPRISES 

LIMITED 

30 CRAVEN STREET, STRAND 

LONDON WC2 



Make 


Model 


Radiol TV 















1970 List now 
available at 2/- 
clus postage 



From .... 
Address 



If list is required 
indicate with X 





enclose remittance of ,.. 

(and a stamped addressed envelope) 
s.a.e, with enquiries please 

MAIL ORDER ONLY (February PW) 



RADIO/TV SERVICE SHEETS 
and MANUALS 

S.A.E. with enquiries please. Mullard 
Valve and Semiconductor Data Book, 
23p, Mazda Valve and Tube Data 
Booklet, 23p, Brimar Valve and Tele- 
tubes Data List, 20p. Resistor Colour 
Code Indicator, 13p. 
BELL'S TELEVISION SERVICES 
Albert Place, Harrogate, Yorks HGI 4QA 
Tel. 0423-86844 

FOR SALE 



MORSE 



MADE 
EASY 



! I 



FACT NOT FICTION. II you start RIGHT 
you will be reading amateur and commercial 
Morse within a month. (Normal progress to 
be expected.) 

Using scientifically prepared 3-speed records 
you automatically learn to reoognise the code 
RHYTHM without translating. You can't help 
it, it's easy as learning a tune. 18 W.P.M. in 
4 weeks guaranteed. 

For details and course C.O.D, ring, s.t.d. 
01-66Q 2886 send 4p stamp tor explantory 
booklet to: 

G3CHS (BOX II). 
45 GREEN LANE, FURLEY, SURREY 



1084 



mi 









*** marine 
r a*o 



wm 



Get*** 



sod 



,o 



TEST ENGINEERS 







•*La4-sH500 



O 



Continuing expansion means we need 
more test engineers with the practical 
experience and real technical knowledge 
to work on the alignment and testing 
ofHF and VHF equipment. 

Theoretical and practical experience 
of semi conductors, SSB and frequency 
synthesis will be a great advantage. 
Age is not important, since initial 
earnings will be directly related to 
experience. 



You could start at £i 144, but with 
more experience this could be in excess 
°Ui5°o. 

Benefits include Pension, Life 
Assurance, 3 weeks holiday. 
Ring or write with brief details to: 
Norman Manion, 
REDIFON LIMITED 
Broomhill Road, Wandsworth, 
London SW18. 01-8747281' 




■ the Htdiffusion O/gjmsjLo,, 






O 



* Xr o ?i - ,T * 



|A 



S *ATlo 



N 









^ *^©ft*tf> h. 






fn,c 3fi©0S /v ? r # : r 3<Ji& 


















1085 



FOR SALE 

(continued) 



/&#&?**** CRN HAMMER 
*inftl ad BLACK WRINKLE 



i u BBc -n. our t 



■ {Cri£hk> 






t Min finish ( 33*f, 

•(JfJT till Oftijr) 7Sp Urri4fC pjBif. 

SPECIAL OFFER: I ua £>| u * cptionU iftim'eir*& I* 
».i*P-an trigger hindJe lvalue IBsufor Qfip , 
pn-d. Chd-ceof 1J WiTajmy plain colour 

*i*r fHc^or rjf d-ujMljr) ilia avjtHible, PIg«* tndom chequ* 
crcisGd P.O. for EOtil arnouni direct to: 
rw-M* Yl I If All 307*, E&G WARE ROAD, 
Ofpt.WR I U IV AN, L0KDOn\VWMBN ^^ 

W* luppty miMy Govttnmtrt Depn-urhent*. 'Mvniuri pil ■ TT^^ 
AudHHTiw.lmiitutri jnd Ladinj Irtftistml Jg t# 

^ Q ryati^jticitit-^W an Hpptf T°v too Wi 

^■< Open 1:1 i"i; im.rd'iy. CJ«wt Thuraday rfi ra neo e.i"| 



SEEN MY CAT? 5,000 items. Mechani- 
cal & Electrical Gear, and material!. 
S.A.E, K. R. WH1STON, DepL PW, 
NEW MILLS, Stockport. 

AUSTRALIAN READERS! SENS 

S.A.E. FOR ELECTRONICS CATA- 
LOGUE. HOBIPAK, P.O. Box 224, Carl- 
ton South, 3053, Victoria, Australia. 



RECEIVERS & COMPONENTS 

AERIAL BOOSTERS 

We make four types of r.f. high gain 
transistorized pre-amplifiers: 

Wideband Radio Type L10 £2.50 
This covers the Medium and 

Short Wave. 

V.H.F. F.M. Radio Type Lll £3 

This covers the V.H.F. radio band. 

V.H.F. Television Type L12 £3 

Please state Band and I and III. 

U.H.F. Television Type L45 £3 

Tunable over the U.H.F. band. 

S.A.E. for Details. 

VALVE BARGAINS 

Any 5—0.45: 10—0.60; 100— £5.50; ECC02, 

ECL80.EF80, EF85, EF183, EBF89, EB91, 

EY86, PCC84, PCC89, PC97, PCF80, 

PCF86, PCL82, PCL83, PCL84, PCL85. 

PL36, PY33, PY81, PY82, PY801, PY8Q0, 

30L15. 

7 day Money Back Guarantee. 

VELCO ELECTRONICS 

62 Bridge St, Ramsbottom, via Bury, 

Lanes. 

BRAND NEW COMPONENTS by re- 
turn. Electrolytics 15 or 25V 1-10 mfd, 
3.5p; 20-100 mfd. 4p; Mylar Film 100V 
.001, .002, .005, .01, .02 2p: .04, .05, .1 
2.5p; Mullard miniature Carbon Film 
Resistors E12 Series i 3 W In-IOMG 8 for 
5p. Postage 5p. The C.R. Supply Co., 
127 Chesterfield Road, Sheffield S8. 



A CORNUCOPIA OF COMPONENTS! 

Scarce valve, selected T.V. compo- 
nents, Speakers, Cabinets. Computer 
panels— long leads NOT printed cir- 
cuits. Transistors, resistors — new and 
recovered. State requirements, S.A.E. 
(F.S.) for details. MAILMART, 6 East- 
bourne Road, Pevensey Bay, Sussex. 



RECEIVERS & COMPONENTS 

(continued) 

Stella Nine Range Cases 

Manufactured in Black, Grey, or Blue 
Stelvetite and finished in Plastic-coated 
Steel, Morocco Finish with Aluminium 
end plates. Rubber feet are attached and 
there is a removable back plate. There is 
also a removable front panel in 1 8 s.w.g 
Alloy. 

Now all Aluminium surfaces are coated 
with a strippable plastic for protection 
during manufacture and transit. All edges 
are polished. 

LIST OF PRICES AND SIZES 
Width Depth 4" Height 6" Height 7±" Height 




£ s. 


d. 


£ s. 


d. 


£ s. 


d. 


15 





18 





1 1 





16 


3 


1 1 


6 


1 S 





IS 





1 5 





1 5 





1 3 





1 11 


9 


1 17 





1 14 


6 


2 2 


6 


2 6 





1 5 





1 11 


9 


1 17 


6 


1 14 





2 2 


Q 


2 5 


f, 


2 3 





2 11 


i 


2 15 


6 


1 10 





I 17 


6 


2 2 





2 11 


6 


3 7 





3 10 





2 6 





2 IS 


6 


3 1 


9 


3 


u 


3 18 





4 6 






Cases — Post 4s. 6d. per order. 
Discounts available on quantities. 

CHASSIS in Aluminium, Standard Sizes, 
frith Gusset Plates 

Sizes to fit Cases. All 2£" Walls 
s. d. s. d. s. d. 

6"x3" 6 6 I0"x7"10 3 14"x3" 8 9 
6-X4" 6 9 12"x3" 8 14"x9" 17 3 
8"x3- 7 9 12"x5" 9 16*x6" 12 9 
8"x6- 9 3 12"x8*l2 9 J6"xlO* 19 

Chassis — Post 3 s. Od. per order. 

Discounts available on quantities. 

E. R. NICHOLLS 

Mtnuftcturtr of Electronic Instrument Ctitt 

46 LOWFIELD ROAD 

STOCKPORT - CHESHIRE 

Tel: 061-480 2179 

MXCROCIBCTJITS 

709 47p 741 88p PA230 92p 

PA234 87p FA237 £1.57 D«C1 67p 

SL402A £1.80 MEL11 47p DIL Conn. 30p 

7410 28p 7420 28p 7430 28p 

TRANSISTORS 

ME0402 21p ME0412 20p ME4101 lip 

ME4102 12p ME6I01 15p MP8111 35p 

2N5172 9p 2N4059 15p 2N3055 65p 

RECTIFIERS 

1N4001 7p 1N40O3 9p 1N4005 12p 

1N4O02 op 1N4004 10p 1N4O06 14p 

PL4002 10p PL4003 lip PL4004 12p 

W005 37p W02 40p PD40 62p 

40583 Diac Trigger Diode 26p 

JEF ELECTRONICS (F.W.4), 

York House, 12 York: Drive, Grappenha.ll. 

Warrington, Lanes. Mall Order Only. C.W.O. 

P.&P. 5p per order. Overseas 40p. 

Money back if not satisfied. 

COMPLETE RANGE of receivers by 
Trio, Lafayette, Hallicr afters, etc. 
Chassis, panels, cabinets. S.A.E. for 
lists. Stephens-James Ltd., 70 Priory 
Road, Liverpool 4. Tel. 051-263 7829. 



Are you thinking of p.W. AMATEUR BANDS 

buiidmg a COMMUNICATIONS RECEIVER 

Save money and time — buy the fujl kit from us to build the second 
converter/i.f. amplifier including chassis for £7-95, the product detector, 
audio amplifier, power supply and s-meter for £9-95. and I.F. amplifier, 
first connector for £7-95 including both chassis. P, & P. 17£p. 

P.W. STEREO TAPE RECORDER 

Excluding case, deck and heads for £19-95 P. & P. 35p. 

F. & B. ELECTRONICS 5, Staple Inn, Hoiborn Bars, W.C.1 

1086 



£5 TELEVISIONS £5 

Delivered anywhere to Great Britiao 
17" 12 channel. Complete & tested. Excellent condition 

Carriage and ins. £1 
17" Untested T.V.s 12 channel tk. GO Carriage £1 , AU makes 

TUBES ! TUBES ! 

Guaranteed 6 months 

17' (43/88 only) «1 M 

19* All makes KM 

23- UM 

l'r* Bonded HA0 

29* Bonded M.S0 

Pins SOp carriage 

SPEAKERS PM 3 ohm perfect ei-T,V. (minimum order 
two) 5* round, 8' by 2T rectangular, 6' by 4" oval— IE j 5 
each. Add 7jp per speaker postage and packaging. 

VALVES EX EQUIPMENT 



EB91 Sp 

EB"F89 12ip 
ECC82 1E}B 

i:e:.?o ?■-> 

EF80 lEip 

■EF35 12 1; 
EF183 ISip 
EP184 lBJtp 



EY86 17tP 
30FL13 20 1 
nSOLZ 12) p 
SOLI 5 lEfp 
30P4 UtP 
PC97 lJ,p 
PCF86 17lp 
PC84 7ip 



On two valves or more 



PCF80 7iB 
POCSB 12 ¥ p 
PCLS5 22ip 
PCL84 17ip 
FCL82 17 T p 
PCL88 171P 
PCL83 l£tl* 
PL38 B8iP 
FL81 17ip 
op postage and 



PT81 Up 
PY80O Up 
PY82 7Jp 
FY33 SHp 
U191 17^p 
6F33 17ip 
30FLI 2T4P 
30P12 80P 
30F3 lip 
packing. 



UHF TUNEEB TO SUIT FBEGTJ8ON 800 900 Chassis 

le-so-i. p. * p. eop 

Dept, T.8. 

THORNBURY TRADE 
DISPOSALS 

Thornbury Kouadaboot, Leeds Bd., Bradiord. Tel. 88 56 70 



5 WATT R.M.S. I.C. (»?av) 



PA246 £2- 



Complete with amplifier details inc. 
how NOT to damage them through misuse 

LOW NOISE HIGH STABS 

i watt 5%, all E24 values from 4.7ft to 

lOMft. 3 for 5d (2p). min. 2 dozen. 

P. & P. on all orders Gp, 

MANY BARGAINS 

SEND FOR LISTS 

CHROMASONIC ELECTRONICS 

56 Fort is Green Road, London, N.10. 



AMERICAN COMPUTER PANELS total 
transistors +30. First Grade Compo- 
nents, Details Transistors supplied. 
3-55p (11/-) post lOp (2/-). Assorted 
Components, 71bs £1-10 (22/-) C.P.— 
J.W.B. Radio, 75 Hayfield Road, Sal- 
ford 6. Mail order only. 

PRINTED CIRCUITS 

PW STEREO TAPE RECORDER (Jan. 

1971). Twin channel — Preamplifiers/ 

Record Amplifiers. Price 65np. Twin 

channel — Monitor Amplifiers. Price 

40p P.&P. 8p. All boards are drilled 

and tin plated with the reverse side 

screen printed for easy component and 

connection identification. S.A.E. for list 

of P.C. boards for other projects. 

"SERVITRON ELECTRONICS" 

18 Beckdean Ave, Poulton-le-Fylde, 

Blackpool, Lanes. FY6 8BG, 

EX-GOVT. COMMUNICATIONS RE- 
CEIVERS, calibrators, signal generators, 

components, etc., with money back guaran- 
tee. SAE list. Callers welcome, please phone 
first.— P. R. Golledse, G3EDW. Glen Tor, 
Torrington. Devon. (STD 084)52) 2411. 



EX COMPUTER PRINTED CIRCUIT PANELS 2m x 

4in packed with semi-conductors and too 
duality resistors, capacitors, diodes, etc. Our 
price, 10 boards 5Gni» + 7no P. & P. With a 
guaranteed minimum of 35 transistors. Data 
on transistors included. 
SPECIAL BARGAIN PACK. 25 boards for CI. 
P. & P. ISno. With a guaranteed minimum of 
B5 transistors. Data on transistors included 



PANELS with 2 Dower transistors similar to 
OC2B on each board + components. 2 boards 
(4 x OC28) 50np + 6no P. & P. 



9 OA5, 3 OAI0, 3 Pot Cores. 26 Resistors. 
14 Caoadtors, 3 GET 872, 3 GET B72B, I GET 
875. All long leaded on panels I3in x 4in. 
4 for £1 + 25np P. & P. 



URGE CAPACITY ELECTROLYTICS 

I0OOOMFD 30V\._ „ , , nnP n P 
I6000MFO |2V/ 40n,> + 6npP - &P - 
or £3.50 per dor. Carr. SOno 



250 MIXED RESISTORS 

± & + watt. 



62 np 



150 MIXED HI STABS 

±. i & I watt 5% and better. 



62 np 



EXTRACTOR/ BLOWER FANS 
(PAPST) 

100 CFM 2800 RPM 4iin x 4+in x 2in Jdea! for 
kitchen extraction, instrument cooling, etc., 
etc. £2.5 + 25np P. & P. 240V AC 5QHz. 



DIODES ex EQPTi SILICON 

I Amo 1000 PIV. 4 forSOnp. 

20 Amp (50 PIV. 4 for £1. + 5np P. & P. 



BARGAIN RELAY OFFER 

Single pole change over silver contacts. 25V 
to 50V. 2.5kft coil. 8 for SOnp 4- Snp P. & P. 



KEYTRONICS mail order only 

52 EARLS COURT ROAD, 
LONDON W8 01-478 8499 



1 ■ r\ ■ W ■ 

WORLD-WIDE RECEPTION 



SHORT-WAVE 
KITS 




F&mnuft for qym 35 yeaiv for Hh.ort*Wdve Equip- 
ment ot quality, "H.A.C 1 were the Original 
eup pliers of Short* Wave Receiver Kits for the 
amateur -constructor. Over 10,000 satisfied 
etmtomers— including: Technical Colleges, Hos- 
pitals, Public Schools, K.AJF., Army, Hams, etc. 

NEW l, DX" RECEIVER 
Improved one-valve model "DX" mark 2. 
Complete kit — price 68^- (post * packing 4/-), 
Customer writes: * 'Austral la, India and America 
at loud volume/'- — "I am 14 years of age and lutve 
logged over 130 stations, plus countless Amateur* 
from all over the world**' 

Send S.A.E. tor teat report* 
This kit -contains all genuine short-wave com- 
ponents, drilled chassis, valve, accessories and full 
Instructions. Heady to assemble, and of course, 
as all our products — fully guaranteed. Frail range 
of other 3.W. kits, including the famous model 
"K" and "K plus" (illustrated above). All orders 
despatched by return. (Mall order only,) Send 
now for free descriptive catalogue & order form. 

"H.A.C." SHORT-WAVE PRODUCTS 
29 Old Bond Street, London W.I 



LADDERS 



VARNISHED TIMBER LADDERS from 
manufacturer. Lowest prices anywhere. 
15' 2 ft. extd. £6-20, 17ft. ext. £6-50, 20ft. 
ext. £7, 21^ ft. ext. £7-75. 241;, ft. ext. 
£8-90. 29ft. ext. £10-25. Sl' 2 ft. triple 
ext. £12-25. 36ft. triple ext. £16. Carr. 
80p, Free lists. Also Aluminium Ext. & 
Loft Ladders. Callers welcome. — (Dept. 
W.L.S.) Home Sales, Baldwin Road, 
Stourport, Worcs. Tel: Stourport 2574. 
Placing order on C.O.D, 



AUDIO EFFECTS 

S SHAW LANE. HALIFAX. YORKS. 

Latest Design— Buy With Confidence From Proven 

Designers. 

Radio Control, 

Single channel T.X. Small compact crystal controlled 
printed circuit. Easy to build and tune. Push Pull QIP 
All silicon transistors. Micro action tune switch. Bottom 
oaded aerial. Coil on P.C board. Fantastic, O/P. Every- 
thing bar case in kit form at 16.0.0 (£11.00) post paid. 
Coils ready wound 10/- (50op) extra- Undrilled alloy 
cose SI- (40np). Beady built in case £8.5.0. (£3.25) post 
paid. 
Super regen RX. 

Miniature, lightweight, supersensitive. Uses pp3 or 
pen cells. Silicon transistors. Front end works straight off. 
O/P without relay (drives actuator direct) or through Ov 
3n0 OHM relay (not provided). Ideal for mode) aircraft. 
In kit form at only £3.5.0. (£3.25) post paid. 
Available Shortly. 

Superhet kit with cascade front end, dual AGC loops. 
Super selective. 

Recommended soldering Iron astex IS watt 3fi,'6 (£1.62.1). 
Ham Band Transistor Superhet Receiver Kit. 

Uses denco plug In coils 500 KHZ to 30 KHZ in 4 
ranges. Normally supplied with kit 1.5 MHZ to 5MHZ 
extra range* 12/- (DOnp) each. Slow motion tuning. 
Posh pull audio output to your 8 OHM speaker black 
perspex. predrilled front panel. In kit form at £9.12.0 
(£0.fi2i) ready built calibrated and guaranteed at £16.5.0 
(£15.25). 
Fo wer Controller. 

Full wave control using branded triac rated 15amp 
3kw. Single control zero to full power. In strong metal 
bos with 13 amp main socket outlet ideal for tires, drills, 
lioodlights, motors etc. Ready built at £9.15.0 (£9.75). 
post paid. In kit form with full instructions £7.5.0. 
(£7.25) post paid. 

Vox Switch. 

Make a noise, it switches, high imp. L/P for XTL mike. 
Drives your 12 volt relay, Ready built £3 .10.0 (£3.50). or 
In kit form £8.7.8. (£2.37 j>. 
Both post paid. 
Reverberation A mplifler. 

Self contained transistorised. Bait operated. Entirely 
different approach to sound reproduction, With this 
unit proper sound delay through reverberation, tones are 
created truly third dimension for concert ball originality. 
Two controls adjust volume and reverberation. Simply 
plug In microphone, guitar etc and O/P into your amplifier 
encased in beautiful walnut cabinet 7i" x 3* X 4i* at 
only £10.15.0 (£10.75) post paid. 
Pocket Metronome. 

Variable beat. Drives your speaker or earpiece pro- 
vided uses pp3. In attractive plastic case at £1,17.8 
(£1.8"1) or as a kit at £1.7,8, (J1.37J) both post paid. 
Morse Oscillator. 

Jost attach your key. Drives your speaker or earpiece 
provided. Works on pen cells. Ready built In case as 
above £1.6,0 (£1.35) as a kit 17/6 (S7i)np both post paid, 
latest Muliard manual on audio amps etc, 82/6 {£1.621) 
postpaid. 

Texas Transistors. Driver NPN and FNP complimentary 
symmetry. Pack of three 7/- (35np) poet paid. 



Fingers 



The more 'fiddly' the job, the 
more you depend on your 
finger-tips. Make sure minor 
burns and blisters don't rob 
them of their skill. 
Apply BURNEZE, pronto! 
This unique scientific aerosol 
cools the heat out of a burn in 
just 8 seconds, anaesthetizes 
pain, reduces swelling. 
BURNEZE - the clever tip for 
burnt finger-tips. 
From chemists. 

/S"S Potter & Clarke Ltd 
\$&) Croydon CR9 3LP 



Est. 1 943 JOHNSONS Tel: 24864 
New! CV2 — a unique triple-purpose 
VHF kit for the Amateur enthusiast. 
Integrated converter, receiver, and 
tuner-feeder. Fantastic single trans- 
istor performance ! Comprehensive kit 
of high grade parts with three coils 
covering 80-1 78M Hz, 9v battery, etc., 
together with simplified diagrams and 
instructions. Price complete, £4, post, 
packing and insurance paid, direct 
from makers. S.A.E. for literature. 

JOHNSONS (RADIO) 

St. Martin's Gate, Worcester 

WR1 2DT 



WHY PAY £60 OB MORE? 



BATTERY MAINS 



COMPLETE FOR 



m 



PORTABLE! £35-50 
RECEIVER ' 




ligh- 

Dowered spotter 

telescope with cash 
order. 



Picks up taxis, 
shipping (VHF 

Transmissions). TV, 
Ambulances, A. A.. 
Pop Pirates, all 
BBC. and Con- 
tinental Stations 
and 1. 300s of 
Public Service 

Transmissions we 
are not allowed to 
mention 

■Jfc 18 Tranaittors 

■*■ 5 Bands 

•k Full 3 year 

OS conditional g'lee. 



Tremend ous value : 
Not just a radio but a 
complete communica- 
tions receiver. Fre- 
quencies: AM 640- 
1800 kes; SW 4-10 

m/cs; FM 88-108 m/cs; Air 108-1*4 m/cs: PSB 143-174 
m/cs. Govern 1,000s Aircraft, Taxi*. Shipping, Badiu 
Hams, TV, Transmissions as well as your favourite radio 
programmes, B.B.C., Pirates, Continents! stations, Auto- 
matic frequeticv control pinpoints stations, locks on and 
eliminates drift, battery operated with built-in adaptor 
for mains supply if required, Completely portable. 
Sup plied with batteries, leal her ease, 8 lze: 10" X 61' X 4". 
Lamp switch, tone switch, Hi-Fidelity earphone, fully 
adjustable telescopic aerial, INSTANT cash refund if not 
satisfied. 

SCIENTIFIC & TECHNICAL SERVICES (Dept. PWI> 

315 London Road, Westcliff, Essex 

(Return of Post Service) 



KEYNECTOR 




Hoad Office and Warehouse 
44A WESTBOURNE GROVE 
LONDON W2 
Ttl. PARK 5641/2/3 



Z & I AERO SERVICES LTD. 



T 



Pleas* send ail correspondence and Mall-Orders to the Head Office 
When sending cash with order, please include 1 2 J np in £ for postage and handling 
MINIMUM CHARGE 12|np. No C.O.D, orders accepted 

Pl.F-ASE NOTE THAI THE VALVES OFFERED BELQVi ARE >OT NECESSARILY OF I'.K. ORIGIN 

PLEASE NOTE THAT ALL PRICES ARE IN DECIMAL PARTS OF €. I.E. IN NEW PENCE 



Rtliil Shop 

15 TOTTENHAM COURT ROAD 

LONDON W1 

Ttl. LANghim MM 

Open all day Saturday 



0A2 0.38 

CIA 3 045 

QB2 0.35 

OB3 0.60 

OC3 0.38 

OD3 0.35 

IB3GT 0.38 

ICF31 6.00 

1 1.4 0.20 



[R4 

IRS 

IS4 
IS5 
IT4 

IU 
IU5 

IV2 



0.35 
0.35 
0.27 
0.25 
0.26 
0.27 
0.50 
0.45 



IX2B 0.40 

2D21 0.35 

3A4 0.35 

3B28 2.15 

3BPI 8.76 

3Q4 0.40 

334 0.SG 

3V4 0.45 

6B4GY 0.60 

5U4G 0,83 

6U4QB 0.42 

6V4G 0.42 

6Y3GT 0.32 

5Z3 0.50 

5Z4G 0.40 

6/30L2 0.75 

6AB4 0.35 

6AF4A 0.50 

6AG7 0.10 

6AH6 0.60 

6AJS 0.30 

6AK3 0,30 

6AK6 0.57 

6AL3 0,43 

r.ALi 0.20 

0AM5 0.32 

GAMS 0.33 

6AQS 0.35 



6AQ6 0.55 
6AR5 0.35 
6AR0 0.40 

6A88 ,0.36 

6AB7G 0.80 
fiATH 0.30 
6AV8 0.25 
6AV6 0.30 
6AW8A 0.55 
6BA6 0.26 



6BE6 
6BF5 
6BFB 

6BH6 

OB.J ') 



0.30 
0.80 
0.50 
0.45 
0.45 



6BK7A 0.65 
6BN6 0.43 
6BN6 0.40 
6BQ0 0.25 



8BWIJ 0.85 

6BW7 0.70 

6BX6 0.25 

6BZ6 0.35 

6C4 0.33 

6C5GT 0.40 

6CAJ 0.28 

ACA7 0.50 

6CB6 0.30 
6CD6GA1.15 

6CQ7 0.50 

GCUU 0.65 

6CL6 0.50 



8CY7 

8D3 

6DC6 



0.65 
0.45 
0.75 



6DK6 0.48 
6DQ6B 0.S3 
6D84 0.75 
6EA8 0.68 
8 EH 7 0.30 
6EJ7 0.36 



6F5 

unit; 

6F11 

6F13 

6F14 

6F15 

GF18 

6F23 

U1--J4 

II E--J5 

6F26 

6F28 

lij ■; 

6J50T 0.30 

■■.it 0.45 

■■k ■■;! 0.55 

6K7 0.35 

8K8G 0.85 

8KS6 0.75 

6L6GT 0.45 

5*71 0.40 

•:-!.i- 0.45 

6LD20 0.40 

6N7GT 0.40 

6P1 

01-JH 



0.85 

0.70 1 

0.60 

0.30 

0.38 

0.38 

0.85 

0.65 

0.45 

0.80 

0.75 

0.76 

0.36 

o.eo 

0.50 



o.so i 

0.50 
0.40 
0.90 
0.50 
0.45 
0.46 
0,60 
0.55 
1.10 



0.60 
0.65 
0.40 
0.40 
0.35 
0.36 



(i*i 17 
03 K7 
6SL7GT0.36 
68X7GT0.S6 
6SQ7 0.40 
08 B 7 0.40 
SIS 0,35 
6C4GT 0.60 
61.' 8 A 0.40 
6X4 0.30 
6X5GT 0.36 
6X8 0.66 
GYGG 0.35 
7Y4 0.80 
SBW6 0.50 



I0C2 
I0D1 
IOD'2 
10F1 
10F9 
10F18 

ioli 

101D1 
10P13 
10P14 

12AB5 0,60 

12AC6 0.40 

12AL5 0.45 

12AQS 0.43 

12 AT 6 0.30 

12 AT 7 0,83 

12ATH 0.30 

12AV7 O.SO 

I2AV6 0.33 

12AV7 0.60 

12AX7 0.30 

1*2 A Y7 0.7O 
12B44 A0.55 

12BA6 0.85 

12BA7 0.35 

I2BE6 0.35 

12BH7 0.40 

12BY7 0.55 

12K5 0.55 
12K7fiT0.S5 

12Q7G 0,30 

12SR7 0.36 

1437 O.SO 



First Quality Fully Guaranteed 



20D1 
SOU 

20P1 
20F4 
i0P5 

'SCO 



0.45 
1.10 
0.60 
L.10 

1.20 
0.50 



25L6GT 0.46 
25Z4G 0.30 
25Z6GT0.65 
30A5 0.46 
30AE3 0.40 
30C1 0.30 




BRAND 



EFS5 
EF8G 
EF89 
EF91 
EF92 
EF95 
EF97 
EF9S 



0.35 

0.30 
0.28 
0.33 
0,40 
0.30 
0.65 
0.65 



ELECTRONIC VALVES 



EF183 0.30 

1CF154 0.35 

EF800 1.00 

EFS01 1.25 

EK90 0.30 



2YS1 
EZ40 
EZ41 

Ezao 

EZB1 



GZ31 
GZ32 
GZ33 
GJS34 



0.43 
0.45 
0.45 
0.25 
0.28 



0.33 
0.48 
0.70 
0.80 



30Ci<3 O.80 
30C17 O.BS 
30C18 0.75 
30F5 0.85 
30FL1 0.70 
30FL12 0.03 
30FL14 0.75 
30 Li 0.40 
30L1S 0.85 
301.17 O.SO 
SOP 12 O.SO 
30F19 0.80 
30PL1 0.70 
30PL13 0.9S 
30 PL 14 0.00 
3oA3 0.56 



35 A 5 
35B5 
33C5 
3505 



0.75 
0.65 
0.40 
0,70 



35L6GT0.50 
35 W 4 O.SO 
35Z3 0.60 
36Z4G 0.80 
35Z5GT0.40 
50A5 0.70 
50B5 0.46 
50CI5 0.40 
50CD6G1.65 
50L8GT0.50 



1.25 
0,60 
3.60 
3.76 
0.76 
0,66 
1,60 
1.60 
2.50 
1.25 
2.15 
0.75 
1.80 
1.26 
1.25 
0.35 
0.50 
0.48 
0.65 
CBL1 O.SO 
CBL31 O.ftO 
CY31 0.85 
DAF96 0.42 
DF96 0.42 
DK40 0.55 
II KM 0.50 



aocv 

807 

81 2 A 

813 

S66A 

5642 

6080 

8146 

G146B 

0360 

6939 

7199 

7360 

7SS6 

7895 

9002 

0003 

AZ1 

AZ31 



DK96 0.42 1 
DMB 0.42 
DM160 0.65 
DY86 0.33 
DY87 0.86 
DY802 0.50 
E88CC 0.66 
E130L 5.00 
E180F 0.05 
EABC80 

0.36 
EAF42 0.66 
EBC33 0.60 
EBC41 0.55 
EBC81 0.30 
EBF80 0.40 
EBF83 0.40 
EBFMi.1 0.30 
EC6 3 0.50 



EC86 
EC88 
EC'.M 
EC91 
EC92 
EC93 



0.60 
0.60 
0.33 
0.60 
0.36 
0.50 



EC8010 2.25 
ECC40 0.00 
ECCS1 0.33 
ECC82 0.30 
ECCS3 0.30 



ECCS4 O.SO 
ECC85 0,60 
ECC88 0.40 
ECC89 0.60 
ECC91 0.20 
ECC1B9 0.60 
ECF80 0.35 
ECF82 0.36 
ECF86 0.66 
ECF8041.60 
ECH42 0.70 
ECH81 0.30 
ECHS3 0.40 
'■'<:' Hi4 0.45 
ECLSO 0.40 
ECL81 0.46 
ECL82 0.3S 
ECLS3 0.66 
ECL84 0.55 
ECL85 0.55 
ECL86 0.40 
K(. 'Li,; 00 

1.50 
EF37A 0.60 
EF39 0.40 



EF40 
KHI 
EF42 
EF80 
EFB3 



0.60 
0.65 
0.70 
0.25 
0.55 



EL33 
EL34 
EL30 
EL37 
EL4I 
EL42 
EL81 
ELS3 
EL84 
EL85 
EI.86 
EL90 



1.25 
0.50 
0.50 
1.25 
0.65 
0.68 
0.6S 
0.12 
0.26 
0.43 
0.40 
0.35 



EL-95 0,36 

ELS 60 1.16 

EL803 1.00 

EL821 0.55 

EL822 0.00 

EI.I.SP 0.76 

EM34 0.00 

EM71 0.76 

EM80 0.40 

EMS1 0.80 

EMS4 0.35 

F.MS 5 1.00 

EM37 0.66 



EYS0 0.46 

EY81 0,40 

EYS3 0.66 

EY86 0,10 



HA1X.S00.45 
HKOO 0.35 
KTfiS 1.70 
KT88 1.75 
N78 1.16 
PABC800.40 
PC86 0.60 
PC88 0.60 
P097 0.50 
PC900 0.48 
PCC84 0.40 
PCC85 0.40 
PCC88 0.55 
PCC89 0.50 
PCC189 0.56 
PCC80S 0.86 
PCO8W0J80 
PCF80 0.30 
PCF82 0.86 
PCF84 0.50 
PCF86 0.60 
PCFS7 0.85 
PCF801 0.60 
PCF802 0.50 
PCF805 0.76 
PCF806 0.70 
PCF808 0.75 
PC II 200 0.70 
PCL81 0.50 
PCL82 O.B5 
PCL83 0.66 
FCLS4 0.45 
PCL36 0.40 
FCL86 0.45 



PCL88 0.90 
PCLSO0 0.03 
PCLSOl 0.70 
PO500 1.60 
FF86 0.80 
PF818 0.86 
PFL2000.70 
PL33 0.36 



PL36 
PL81 
PL82 
PLA3 
PL84 



0.56 
0.50 
0.46 
0.45 

1.10 



L'7S 

47191 

U201 

U281 

(-2S2 

U301 

U403 

U404 

U801 



0.30 
0.76 
0.36 
0.40 
0.40 
0.40 
0.50 
0.40 
1.00 



PL302 O.SO 

FL504 0.80 

PL508 0.90 

PL609 1.80 

PL509 1-30 

PL801 0.80 

PMS4 0,60 



PY31 
PY33 
r v SO 
FYai 



0.30 
0.S3 
0.35 
0.30 



PY82 O.SO 
PY83 0.88 

PYS8 0.40 
PY500 1.00 
PY800 0.60 
PY801 0.50 
PZ30 0.S6 
QQV2-6 S.16 
QQVO3-I0 

1.B5 
QCJV03-20A 
I 5.25 

I TT21 2.65 
I TT22 2.80 
I U 18/20 0.76 
0.75 



LI 26 
U31 
U37 
U52 
U76 



0.75 
0.45 

1.50 
0.33 
0.30 



UABC80 

0.36 
UAF41 OJO 
UAF42 0.56 
TJBC41 0.60 
UBC81 0.40 
UBFB0 0.40 
UBFS9 0.35 
UBL1 0.60 
UBL21 0.00 
UC92 0.35 
UCC88 0.40 
UCF80 0.66 
UCH21 0.80 
UCH42 0.70 
VCK43 0.76 
UCB81 0.85 
1JCI.81 0.60 
UCL82 0.35 
UCLS3 O.SO 
UF41 0,60 
17F42 0.60 
UF43 0.60 



UF80 
UP85 

t tat 

TJL41 
TJB84 



0.35 
0.40 
0.35 
0.85 
0.30 



UM84 0.20 
CY1N 0.50 



TJYU 
UY41 
UY8i 



0.65 
0.45 

0.60 



UY8B 0.80 
W729 0.60 



TRANSISTORS 



._ 



2K404 
2S444A 

2S696 
2N697 
2N698 
2N706 
2S706 
2S70B 
2N753 
2N929 
2N930 
2X987 
2X1131 

aNiisa 

2N1184 

2X1301 

2X1302 

2K1304 

2X1305 

2N1306 

2X1307 

2X1306 

2X1309 

2N1613 

2N1711 

UN 175 6 

2N2147 

2S2160 

2X2217 

2N2218 

2N2219 

UN2369A 

2N2477 

2S2646 

SN2906 

SHSOSS 

2X2924 

2N2926 

2X3053 

2N305S 

2S3133 

2X3134 

2N3391 

2K3392 

2X3393 

2X3394 

2X3395 

2X8402 

2X3403 

2X3404 

2X3414 

2N3415 

2N3416 

2N3417 

2N3702 

2X3703 

2X3704 

2X3707 

2X3709 

2N3710 

2N38I9 

2X3906 

28002 

2BO04 



1088 



0.17 
0.26 
0.20 
0.2S 
0.40 
0.70 
0.16 
0.20 
0.25 
0.30 
0.35 
0.35 
0.40 
0.46 
1.26 
0.40 
0.26 
0.25 
0.25 
0.25 
0.30 
0.40 
0.35 
0.25 
0.30 
0.75 
0.75 
1.25 
0.30 
0.40 
0.46 
0.25 
0.66 
O.SO 
0.60 
0.15 
0.15 
0.15 
O.SO 
0.75 
0.35 
0.50 
0.20 
0.16 
0.15 
0.16 
0.20 
0.15 
0.15 
0.35 
0.20 
0.15 
0.25 
0.26 
0.15 
0.16 
0,20 
0.20 
0.15 
0.15 
0.35 
0.30 
1.00 
1.00 



23034 

23102 

28104 

23701 

2S702 

23746 

AC113 

AC125 

AC 126 

AG127 

AC 132 

AC 153 

AC 15 4 

AC 156 

AC1E7 

AC169 

AC 176 

AC 187 

AC1S8 

ACY17 

ACY1B 

ACY19 

ACY20 

ACY21 

ACY22 

AD140 

AD149 

AD161 

AIH02 

AF114 

A I' 110 

AFU6 
AF117 
AF118 
AF125 
AF127 
AF178 
AF180 
AF181 
AF18G 
AF239 
AFZ11 
AHY26 
A3Y27 
A8Y28 
A8Y29 
A8Y64 
ABY74 
A3Y77 
ABY82 
A8Y86 

ASZI8 

AHZ17 
A8Z18 

iSZ'Jl 

BC107 
BC10S 
BC109 
BC113 
BC118 
BC134 
BCH7 
BC148 
BC149 



1.00 
0.40 
0.50 
0.60 
0.60 
0.30 
0.16 
0.80 
0.25 
0.20 
0.36 
0.26 
0.16 
0.23 
O.SO 
0.10 
0.26 
0.30 
0.80 
0.30 
0.20 
0.26 
0,20 
0.E0 
0.15 
0.S0 
0.50 
0,35 
0.36 
0.25 
0.30 
0,25 
0.20 
0.45 
0.25 
0.25 
0.40 
0.35 
0.85 
0.60 
0.40 
0.4S 
0.26 
0.30 
0.30 
0.30 
0.25 
0.50 
0,36 
0.20 
0.20 
0.70 
0.75 
0.75 
0.6O 
0.15 
0.15 
0.20 
0.40 
0.80 
0.80 
0.20 
0.15 
0.16 



BC152 

BC175 

BCY30 

BCY33 

BCY34 

BCY72 

BCZ11 

BD121 

BD123 

BF115 

BF197 

BF173 

BF181 

BF184 

BF186 

BF194 

SF196 

BF196 

BF197 

BFW87 

BFW88 

BFTV89 

BFW91 

BFX88 

BFY17 

BFY19 

BFV50 

BFY61 

BFY62 

B8Y28 

B8Y27 

BSY28 

B9Y66 

BBY95A 

OC16 

OC22 

OC23 

OC24 

OC26 

OC26 

OC28 

OC29 

OC30 

OC30 

OC36 

OC4B 

OC44 

OC46 

OC70 

OC71 

OC72 

OC73 

OC75 

OC76 

OC78 

OC78D 

OC81 

OC81D 

OC83 

OC139 

OC110 

OC141 

OC170 

OC171 



0.16 
0.S5 
0.35 
0.26 
0.80 
0.20 
0.40 
O.SO 
0.S& 
0.20 
0.26 
0.30 
0.25 
0.25 
0.20 
0.20 
0.15 
0.20 
0.20 
0.30 
0.25 
0.28 
0.20 
0.25 
0.40 
0.60 
0.26 
0.20 
0.26 
0,26 
0.30 
0.30 
0.20 
0.20 
0.75 
0.65 
0.60 
0.60 
0.40 
0.30 
0.60 
0.86 
0.75 
0.60 
0.80 
0.30 
O.EO 
0.20 
0,20 
0.16 
0.25 
0.40 
0.26 
0.25 
0.25 
0.20 
0.25 
0.16 
0.20 
0.35 
0.40 
0.60 
0.26 
0.26 



SYNCHROSCOPE TYPE C1-5 




3-ln tube fitted with telescopic viewing hood, giving 

bright dlaplaj in full daylight. 

Bandwidth 10 ert— 10 mc/i. Triggered jweep pre-»et at 

1-2 -G-l 0-30-1 00-3 00- 1000- 3000 (inec per stroke. Fnee- 

rannlng time base 20 c'» to 2000kcrt with built-in 

crystal calibrator providing timing marks at .05 -. 2-1-5- 

20' 100 p sec + 6%. 

Amptitude calibrator directly calibrated In Tolls. 

Input attenuator 1-10-100. 

Powersupplieal27/230TAC. 

PKICE {39.00. Packing and carriage 1.50 



MtNLATORE 1-DI CATHODE RAY TUBE 
TYPE DHS-91— 10F1— 1CP3L 

63v heater. Anode voltage 500 v. Sensitivity Y plates 
ISvjcui; X plates S2Wcm (typical) Y plates suitable iur 
asaym metrical deflection. Green face, medium persistence. 

PRICE £8.0.0 p.p. 0.26 



SOLID STATE LIGHT EMITTIBO 
DIODES MV10B 

T018 outline. Brightness 500 FT-L at 50mA. Forward 
voltage 1-65 to 2V, Diode gives bright red pinpoint, of 
light when suppSied from a SV source. Lens dlainrter 
0170ln. PRICE (1.05 



OTJB NEW 1970H971 CATALOGUE IS NOW BEADY 
AND AVAILABLE FREE OF CHARGE. PLEASE 
BEND QUARTO STAMPED AND ADDBESSED 
ENVELOPE FOE THIS VALUABLE SOURCE OF 
REFERENCE LISTING MAS" Y THOUSAND TYPE3 
OF VALVES, SEMICONDUCTORS. TUBES ETC. 



TWO NEW MULTIMETERS 
FROM RUSSIA 



Type U43I2 
U43I3 

with AC c orient ranges 

Type U4812— Low sensi- 
tivity instrument (667 
o.p.v.) 1 % accuracy Oh 
DC »nd 1-5% on AC. 9 current ranges on DC (300f£A to 6A) 
and 8 current ranges on AC (1 -SniA to 8A). voltane ranges 
0-3 to 900V AC/DC. Resistance 0-2 to 30k fl. Mirror scale, 
PBICE, complete with leads and steel carrying case £9-76 
Type 174818— 20,000 o.p.v. DC and 2,000 o.p.v, on AC. 
8 DC current ranges OOflA to 1 B A. 6 AC current ranges 
0'6 to 1-6A. 9 DC antl AC voltage ranges 1 ■5-500 V. Resist- 
ance ranges OS-SOOkQ. Accuracy 1-5% DC and 2-5% AC. 
Mirror scale. 
PRICE, complete with test leads and steel carrying caw 

110.60 




aUjnATTJRE CERAMIC CAPACITORS 26V WORBMO 

5% tolerance 22-27-33-39-47-456-68-82-100-120-180- 

180-220-270-33 -390-470 -5 60-680-82O- lOOOpF 

All at 18np per dozen. 
+ B0%-20% tolerance 1500-2 200-3300-1700-6800- 10,000 

-15,000 pF— All at 15np per dozen. 
+ 80 %-20 % tolerance 0.022-0, 033-0.047 n V. 

All at EOnp per dozen. 
Minimum orders 12 of one size. 



HALF WAVE 8HJCOH WISE ENDED EECTIFIER8 



BY 101 
154002 
BY 125 
IN 4004 
BY ISO 
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IN4006 
BY 105 



50 p.i.v. 
100 p.i.v. 
200 p.i.v. 
400 p.i.v. 
450 p.l-v- 
600 p.i.v. 
800 p.i.v, 
800 p.i.v. 



1 Amp 
1 Amp 
425mA 
1 Amp 
800 mA 
1 Amp 
1 Amp 
l'l Amp 



lOnp 
lOnp 
ISnp 
12np 
lOop 
15ns 
15np 
20np 



JXTEQ RATED MOKOLTTHIC DUAL OPERATIOKAL 
AMPLIFIER MC14S6F 

Two identical amplifiers in 14-pln dual-lD-llne epoiy 
package. 400tnW dissipation. Typical open loop voltage 
gain 7000. Mai. differential input ± SV. Power suppllee 
6 to 9V, Max. frequency 1 mc/s. 18.00. 



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HI-FI COMPONENTS • TEST • PA • DISCOTHEQUE ■ ELECTRONIC ORGANS ■ MAIL ORDER 



TRANSISTOR 
AMPLIFIERS 

NEW RANGES NOW IN STOCK 

{Leaflets Ref. No, 6 and 8) 

Post etc. 20 p (4/- J 

4-300 4 TR 9V 3O0mW £1 -79 (35/-) 



£2-12(42/5) 
£2-47 (49/5) 
a -75 (55/-) 
a -62 (72/5) 
£4-12 (82/5) 
£4-97 (99/5) 



104 4TR 9V 1W 
304 4TR 9V 3W 
555 6 Tft 12V 3W 
PA7 6 TR 16V 7W 
609 6 TR 24V I OW 
410 4 TR2BV I0W 
MPAI2/3 6 TR 18V I2W £4-50 {90/-} 
MPAI2/IS6TR36VI2W£S-2S (105/-) 
Z30 9 TR 30V 20W £J-75 (75/-) 
PA25 10 TR (Spl) 25 W £7-50 (ISO/-) 
Z50 30V40W £5-47(109/5) 

PASO I2TR (Spl) SOW £9.50(190/-) 
100 IOOW with Power Supply £45 -00 
Post 4Sp (9/-) 

OPTIONAL POWER SUPPLIES 

Post etc. 20 p (4/-). 

P.SOOSwitehable (One or Two) For 104. 304 
PS.20 Switchable (One or Two) for PA7 
MU24/4Q Switchable (One or Two) for MPA 12/3 

or MPA 12/ 1 5 
PZ5 for Z30 £3-97 (79 /S) or PZ6 for Z30 
PZ8 for ZSO £5-97 (1 19/S) Transformer 
PI I for 608 £2-87 (57/5) PIS for 410 
MU442 for I or 2 PA2S or I only PA50 




£4-50 (90/-) 
£6-97 (139/5) 
£2-15 (45/-) 
£2-62 (52/5) 
£6-50(130/-) 



SINCLAIR PROJECT 60 PACKAGE DEALS 
2xZ30 amplifier, stereo 60 pre-amp, PZ5 power supply. £19. 
Carr. 40p. Or with PZ6 power supply £21. Carr. 40p. 2xZ50 
amplifier, stereo 60 pre-amp. PZ8 power supply. £21-50. 
Carr. 40p. Transformer for PZ8 £2.25 extra. Any of the above 
with Active Filter unit add £4.87 or with pair QI6 speakers add 
£16. Also new FM Tuner £23. 



BUILD THIS VHF FM TUNER 

5 MULLARD TRANSISTOR5 300 
kc/s BANDWIDTH. PRINTED CIR- 
CUIT. HIGH FIDELITY REPRO- 
DUCTION. MONO AND STEREO. 
A popular VHF FM Tuner for quality 
and reception of mono and stereo. 
There is no doubt about it — VHF FM 
gives the REAL sound. All parts sold 
separately. 

Free Leaflet No. 3 & 7. TOTAL £6-97 (£6.19.6) p.p 20p (4/-) 
Cabinet lOOp, Decoder Kit £5.97, Tuning meter £ 1 .75 
Mains unit (optional) Model P5900 £2-47 (49/5) 
Mains unit for Tuner and Decoder PS 1 200 £2-62(52/5) 




HI-FI TO SUIT 

EVERY 
POCKET 




CHOOSE 1AA STEREO 
FROM '""SYSTEMS 

and a complete ranee of 
individual units in stock — 
Demonstrations all day — 
visit our new Hi Fi Score. 
LOW CASH OR CREDIT/ 
HP TERMS (Credit terms 
from £30 purchase — callers 
only). 

FREE Stock list No. 

16, 17 on request — BEST 
VALUE IN U.K. 




BUILD YOURSELF A QUALITY RADIO 



Excellent printed circuit design with 
full power output. Fully tuneable on 
both MW/LW bands. 7 Muflard tran- 
sistors. Fitted Sin. speaker. Room 
filling power. Easy to build with terrific 
results. Two colour leather-cloth 
cabinet with silvered front. All local 
and continental stations. Complete 
detailed instructions. 
Total cost £6-98 (£6. 19.6). p.p 35p (7/-), 
All parts sold separately. 




Ask For leaflet No 



HENRY'S LATEST 
CATALOGUE 

Now 350 

pages, 
WHY 
NOT 
SEND 
AWAY 
TODAY 

ic COMPONENTS, TEST 

GEAR 
* EQUIPMENT. MODULES 
ir SPECIAL OFFERS, etc. etc. 

Everything for the construc- 
tor. Complete with 50p value 
discount voucher for use with 
purchase. Price 50p Post Paid. 



8 page Transistor, 

IC. Diode lists 

No. 36 

20 page Organs to 

Build brochure 

No. 9 

Decks and Hi Fi 

Stock Lists No, 

16/17 

PA, Disco and 

Lighting List No, 

13 

Quotations for all 

Electronics — send 

list and S.A.E. 



FREE 
FREE 
FREE 
FREE 
FREE 



TEST EQUIPMENT FOR HOME, 

SCHOOL & PROFESSIONAL USE 

AFI05 50k/volt multimeter (ill us.). 

Price £8-50 (1 90/-),p.p 20p (4/-)- Leather 

case £ I -42 (28/5). 

200H 20k/volt, 

Price £3-87 (77/5), p.p 20p (4/-). Case 62p 

(12/5). 

500 30k/volt mutti-meter. 

Price £8-87 (177/5), p.p 20p (4/-). 

Leather case £1.50 (30I-). 

THL 33 2k/volt. 

Price £4-11(82/5). p.p I5p (3/-). 

Leather case £1.15 (23/-) 

TE65 Valve voltmeter (illus.) 

Price £17-50 £17.10.0). p.p 40p (8/-). 

SE250B Pocket pencil signal 

injector. Price £t.7S Post 

Paid. 
SE500 Pocket pencil signal tracer. Price £1-50 
Post Paid. 

TE20D RF generator Price £15. p.p 40p (8/-) 
TE22D Matching audio generator. 
Price £17. p.p 40p (8/-). 

TEI5 Grid dip meter. Price £12-50. p.p 40p 
T03 Scope 3* tube. Price £37-50. p.p 50p. 
TE22 Audio Generator £17. p.p 40p (8/-) 
(GET A COPY OF OUR LATEST CATALOGUE FOR FULL 
SPECIFICATIONS AND FURTHER RANGES). 





NEW 

MINIATURE 
LOW COST 
AMPLIFIER 



MODEL 4-300 
9 volt operated or mains unit optional 
transformer (MT98 70p (14/-) ). i-IOmV 
adjustable sensitivity. P/P output for 
3-8 ohms. Fitted volume control and 
leads. Size 5t" * I tt" X J". Thousands 
of uses — takes magnetic, dynamic and 
crystal inputs direct. Output 3O0mW — 
very high gain— built in rectifier circuit. 




PRICE £1.75 

(35/-) p.p iSp (3/-). 

Complete with 

FREE leaflet No. B. 



STCTIME DELAY 
MODULE 




Ideal for experimen- 
ters, educational pro- 
jects as well as /or 
practical uses. Delay 
adjustable 3-15 sees. 
Operates 9-12 volts. 
Heavy Duty Relay 
Contacts. Complete 
with suggested appli- 
cations sheet. Price 
£I-7S(3S/-). PostPaid. 



GARRARD 
TAPE DECK 




9 vole operated 2-speed tape 
deck fitted! Record /Rep lay i track 
and Erase/Bias Osc. Head. Com- 
plete with Oscillator/Record head 
circuit. Unit ske 9" X 6J* X l&" 
and 2i" below motor board. Takes 
up co 4* spook. Supplied Brand 
New, 



HENELEC SELF-POWERED PRE-AMPLIFIERS 




SLIM MODERN DESIGNS USING 
THE LATEST SILICON TRANSISTORS 
FET's and IC's, DIN SOCKETS. Etc. 
fitted. Self powered. 
PUSH-BUTTON SELECTION, ±20dB 
BASS AND TREBLE BOOST & CUT 
All inputs provided plus TAPE 
RECORD and REPLAY. 



Designed for use with PA25 and PA50 
Amplifiers GOLD AND SILVER 
FINISH, Mains operated. Supplied with 
all plugs, etc. ADJUSTABLE OUTPUT 
UP TO I VOLT. 

* FET9/4. Mono with built-in mic. 
mixer. Accepts any ceramic or crys* 
tal cartridge. Plus tuner, tape, etc. 
Price £12-50 (£ 1 2. 10.0) p.p 20 p (4/.), 

* FETI54 STEREO (illus.). 
Magnetiecart. input, tuner, tape, etc 
Beautiful stereo sound. 

Price £16-50 (£16. 10.0). p.p 25p (5/-) 

Also suitable far use with any power 
amplifier. Suggested types PA25. PA50, 
MPA/2/3. MPAI2H5 



IS WATT AND 50 WATT 
SILICON AMPLIFIERS 

LOOK AT THE SPECIFICATIONS 

•fa At full power 0.1% distortion. 

ir At full power — I dB I Ic/i to 40 kc/s, 

•Jr Response- IdB II c/s to 100 kc/s. 

• Rise tim. !„«<, FREE LEAF| _ ET 

^t Short circuit proof No. 25 on request 
plus limiting cce. 

PA 25 10 transistor all silicon differential input 400m V sensitivity. 25 watts Rms 

into 3 ohms. Supplied with edge connector harness size 5* x 3* X 2*. 

PA 50 12 transistor version 50 watts Rms into 3 to 4 ohms. Size 5* X 3* x 4*. 

MU 442. Power supply or one or two PA. 25 or one PA 50 

PA 25 £7-50; PA 50 £9-50. MU 442 £6.00 P. & P. 20p each. 




SIMPLICITY TO MOUNT— EASY TO USE— DESIGNED FOR QUALITY, PERFORMANCE AND PRICE 

Ail ....tit. „„ --««-. » - ■ _«. _j„„ „«__„«.,._. - J 1 AS SPECIFIED FOR MANY "PRACTICAL WIRELESS" 1970 

II units no soldering— just edge connectors and plugs projects 



Electronic Components & 
Test Gear Centre 
356 EDGWARE ROAD, 
LONDON, W.2. 
Tel: 01-402 4736 



High Fidelity Sales & Electronic Organs, 

Demonstrations Centre PA. & Discotheque Centre 

354 EDGWARE ROAD, 309 EDGWARE ROAD, 

LONDON, W.2. LONDON, W.2. 

Tel : 01 -402 S8S4 Tel : 01 -723 6963 



Mail Orders. Special 
Shop, Industrial Sales 
303 EDGWARE ROAD, 
LONDON, W.2. 
Tel: 01 -723 1008/9 



to 6pm. MONDAY TO SATURDAY — 9 a.m. to 7 p.m. THURSDAYS — OPEN ALL DAY SATURDAY